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	$33.55	11.302%	$37.3418	$37.34	$37.35	$37.30
Purchase #2	$168.32	4.244%	$175.4635	$175.46	$175.45	$175.50
Purchase #3	$104.74	5.429%	$110.4263	$110.43	$110.45	$110.40
Purchase #4	$154.68	3.405%	$159.9469	$159.95	$159.95	$159.90
Purchase #5	$32.86	13.871%	$37.418	$37.42	$37.40	$37.40
Purchase #6	$220.48	10.336%	$243.2688	$243.27	$243.25	$243.30
Purchase #7	$246.66	12.755%	$278.1215	$278.12	$278.10	$278.10
7 purchase totals =	$961.29		$1,041.9868	$1,041.99	$1,041.95	$1,041.90