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	$48.39	9.756%	$53.1109	$53.11	$53.10	$53.10
Purchase #2	$236.73	7.764%	$255.1097	$255.11	$255.10	$255.10
Purchase #3	$66.83	5.195%	$70.3018	$70.30	$70.30	$70.30
Purchase #4	$246.84	13.232%	$279.5019	$279.50	$279.50	$279.50
Purchase #5	$247.99	4.495%	$259.1372	$259.14	$259.15	$259.10
Purchase #6	$22.51	12.584%	$25.3427	$25.34	$25.35	$25.30
Purchase #7	$73.56	13.199%	$83.2692	$83.27	$83.25	$83.30
7 purchase totals =	$942.85		$1,025.7734	$1,025.77	$1,025.75	$1,025.70