Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$242.51	9.172%	$264.753	$264.75	$264.75	$264.80
Purchase #2	$77.55	11.358%	$86.3581	$86.36	$86.35	$86.40
Purchase #3	$121.56	4.734%	$127.3147	$127.31	$127.30	$127.30
Purchase #4	$155.54	12.510%	$174.9981	$175.00	$175.00	$175.00
Purchase #5	$112.37	13.593%	$127.6445	$127.64	$127.65	$127.60
Purchase #6	$43.32	8.158%	$46.854	$46.85	$46.85	$46.90
Purchase #7	$41.93	6.500%	$44.6555	$44.66	$44.65	$44.70
7 purchase totals =	$794.78		$872.5779	$872.57	$872.55	$872.70