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	$22.59	9.614%	$24.7618	$24.76	$24.75	$24.80
Purchase #2	$148.67	7.396%	$159.6656	$159.67	$159.65	$159.70
Purchase #3	$226.45	12.814%	$255.4673	$255.47	$255.45	$255.50
Purchase #4	$73.65	9.459%	$80.6166	$80.62	$80.60	$80.60
Purchase #5	$246.89	9.753%	$270.9692	$270.97	$270.95	$271.00
Purchase #6	$199.82	6.382%	$212.5725	$212.57	$212.55	$212.60
Purchase #7	$85.40	12.733%	$96.274	$96.27	$96.25	$96.30
7 purchase totals =	$1,003.47		$1,100.3270	$1,100.33	$1,100.20	$1,100.50