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	$133.95	7.817%	$144.4209	$144.42	$144.40	$144.40
Purchase #2	$172.51	6.688%	$184.0475	$184.05	$184.05	$184.00
Purchase #3	$18.50	11.228%	$20.5772	$20.58	$20.60	$20.60
Purchase #4	$125.56	11.294%	$139.7407	$139.74	$139.75	$139.70
Purchase #5	$235.88	11.562%	$263.1524	$263.15	$263.15	$263.20
Purchase #6	$144.96	11.137%	$161.1042	$161.10	$161.10	$161.10
Purchase #7	$115.89	13.821%	$131.9072	$131.91	$131.90	$131.90
7 purchase totals =	$947.25		$1,044.9501	$1,044.95	$1,044.95	$1,044.90