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	$165.76	3.287%	$171.2085	$171.21	$171.20	$171.20
Purchase #2	$38.95	12.766%	$43.9224	$43.92	$43.90	$43.90
Purchase #3	$143.46	13.352%	$162.6148	$162.61	$162.60	$162.60
Purchase #4	$93.93	10.382%	$103.6818	$103.68	$103.70	$103.70
Purchase #5	$118.98	7.338%	$127.7108	$127.71	$127.70	$127.70
Purchase #6	$206.72	8.189%	$223.6483	$223.65	$223.65	$223.60
Purchase #7	$130.40	6.388%	$138.73	$138.73	$138.75	$138.70
7 purchase totals =	$898.20		$971.5166	$971.51	$971.50	$971.40