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	$237.61	11.422%	$264.7498	$264.75	$264.75	$264.70
Purchase #2	$67.63	6.163%	$71.798	$71.80	$71.80	$71.80
Purchase #3	$221.48	8.389%	$240.06	$240.06	$240.05	$240.10
Purchase #4	$51.99	10.240%	$57.3138	$57.31	$57.30	$57.30
Purchase #5	$13.51	4.709%	$14.1462	$14.15	$14.15	$14.10
Purchase #6	$114.70	5.345%	$120.8307	$120.83	$120.85	$120.80
Purchase #7	$153.48	12.322%	$172.3918	$172.39	$172.40	$172.40
7 purchase totals =	$860.40		$941.2903	$941.29	$941.30	$941.20