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	$33.99	3.228%	$35.0872	$35.09	$35.10	$35.10
Purchase #2	$233.95	7.462%	$251.4073	$251.41	$251.40	$251.40
Purchase #3	$182.51	3.624%	$189.1242	$189.12	$189.10	$189.10
Purchase #4	$81.62	12.192%	$91.5711	$91.57	$91.55	$91.60
Purchase #5	$92.57	6.691%	$98.7639	$98.76	$98.75	$98.80
Purchase #6	$99.76	12.193%	$111.9237	$111.92	$111.90	$111.90
Purchase #7	$133.25	13.660%	$151.452	$151.45	$151.45	$151.50
7 purchase totals =	$857.65		$929.3294	$929.32	$929.25	$929.40