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	$129.71	9.153%	$141.5824	$141.58	$141.60	$141.60
Purchase #2	$183.29	10.375%	$202.3063	$202.31	$202.30	$202.30
Purchase #3	$48.39	6.362%	$51.4686	$51.47	$51.45	$51.50
Purchase #4	$91.92	8.383%	$99.6257	$99.63	$99.65	$99.60
Purchase #5	$62.72	12.554%	$70.5939	$70.59	$70.60	$70.60
Purchase #6	$178.34	6.318%	$189.6075	$189.61	$189.60	$189.60
Purchase #7	$105.82	7.466%	$113.7205	$113.72	$113.70	$113.70
7 purchase totals =	$800.19		$868.9049	$868.91	$868.90	$868.90