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	$40.53	12.594%	$45.6343	$45.63	$45.65	$45.60
Purchase #2	$147.31	12.355%	$165.5102	$165.51	$165.50	$165.50
Purchase #3	$236.48	7.279%	$253.6934	$253.69	$253.70	$253.70
Purchase #4	$188.96	13.755%	$214.9514	$214.95	$214.95	$215.00
Purchase #5	$239.93	13.605%	$272.5725	$272.57	$272.55	$272.60
Purchase #6	$196.38	13.695%	$223.2742	$223.27	$223.25	$223.30
Purchase #7	$45.68	5.229%	$48.0686	$48.07	$48.05	$48.10
7 purchase totals =	$1,095.27		$1,223.7046	$1,223.69	$1,223.65	$1,223.80