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	$118.89	10.490%	$131.3616	$131.36	$131.35	$131.40
Purchase #2	$243.79	10.729%	$269.9462	$269.95	$269.95	$269.90
Purchase #3	$28.58	11.398%	$31.8375	$31.84	$31.85	$31.80
Purchase #4	$149.31	12.219%	$167.5542	$167.55	$167.55	$167.60
Purchase #5	$235.59	8.329%	$255.2123	$255.21	$255.20	$255.20
Purchase #6	$133.64	13.389%	$151.5331	$151.53	$151.55	$151.50
Purchase #7	$175.54	5.131%	$184.547	$184.55	$184.55	$184.50
7 purchase totals =	$1,085.34		$1,191.9919	$1,191.99	$1,192.00	$1,191.90