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	$212.34	13.683%	$241.3945	$241.39	$241.40	$241.40
Purchase #2	$192.58	8.602%	$209.1457	$209.15	$209.15	$209.10
Purchase #3	$175.32	11.830%	$196.0604	$196.06	$196.05	$196.10
Purchase #4	$235.84	5.630%	$249.1178	$249.12	$249.10	$249.10
Purchase #5	$201.39	8.828%	$219.1687	$219.17	$219.15	$219.20
Purchase #6	$200.29	10.395%	$221.1101	$221.11	$221.10	$221.10
Purchase #7	$137.47	11.164%	$152.8172	$152.82	$152.80	$152.80
7 purchase totals =	$1,355.23		$1,488.8144	$1,488.82	$1,488.75	$1,488.80