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	$20.72	9.861%	$22.7632	$22.76	$22.75	$22.80
Purchase #2	$26.73	10.655%	$29.5781	$29.58	$29.60	$29.60
Purchase #3	$134.86	10.413%	$148.903	$148.90	$148.90	$148.90
Purchase #4	$197.27	5.761%	$208.6347	$208.63	$208.65	$208.60
Purchase #5	$240.95	11.311%	$268.2039	$268.20	$268.20	$268.20
Purchase #6	$152.37	13.199%	$172.4813	$172.48	$172.50	$172.50
Purchase #7	$203.93	9.769%	$223.8519	$223.85	$223.85	$223.90
7 purchase totals =	$976.83		$1,074.4161	$1,074.40	$1,074.45	$1,074.50