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	$159.47	5.165%	$167.7066	$167.71	$167.70	$167.70
Purchase #2	$118.80	10.427%	$131.1873	$131.19	$131.20	$131.20
Purchase #3	$22.51	4.762%	$23.5819	$23.58	$23.60	$23.60
Purchase #4	$55.54	5.457%	$58.5708	$58.57	$58.55	$58.60
Purchase #5	$104.35	6.424%	$111.0534	$111.05	$111.05	$111.10
Purchase #6	$165.54	4.645%	$173.2293	$173.23	$173.25	$173.20
Purchase #7	$32.38	8.391%	$35.097	$35.10	$35.10	$35.10
7 purchase totals =	$658.59		$700.4263	$700.43	$700.45	$700.50