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	$53.98	13.488%	$61.2608	$61.26	$61.25	$61.30
Purchase #2	$62.31	11.397%	$69.4115	$69.41	$69.40	$69.40
Purchase #3	$34.81	4.739%	$36.4596	$36.46	$36.45	$36.50
Purchase #4	$144.52	10.283%	$159.381	$159.38	$159.40	$159.40
Purchase #5	$86.55	4.624%	$90.5521	$90.55	$90.55	$90.60
Purchase #6	$49.59	5.528%	$52.3313	$52.33	$52.35	$52.30
Purchase #7	$232.99	7.196%	$249.756	$249.76	$249.75	$249.80
7 purchase totals =	$664.75		$719.1523	$719.15	$719.15	$719.30