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	$181.59	11.865%	$203.1357	$203.14	$203.15	$203.10
Purchase #2	$48.31	12.479%	$54.3386	$54.34	$54.35	$54.30
Purchase #3	$223.94	8.831%	$243.7161	$243.72	$243.70	$243.70
Purchase #4	$250.45	10.533%	$276.8299	$276.83	$276.85	$276.80
Purchase #5	$112.51	5.134%	$118.2863	$118.29	$118.30	$118.30
Purchase #6	$159.65	9.216%	$174.3633	$174.36	$174.35	$174.40
Purchase #7	$169.96	9.115%	$185.4519	$185.45	$185.45	$185.50
7 purchase totals =	$1,146.41		$1,256.1218	$1,256.13	$1,256.15	$1,256.10