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	$245.66	3.105%	$253.2877	$253.29	$253.30	$253.30
Purchase #2	$44.85	13.251%	$50.7931	$50.79	$50.80	$50.80
Purchase #3	$40.61	11.793%	$45.3991	$45.40	$45.40	$45.40
Purchase #4	$156.36	7.143%	$167.5288	$167.53	$167.55	$167.50
Purchase #5	$198.83	5.689%	$210.1414	$210.14	$210.15	$210.10
Purchase #6	$166.65	11.700%	$186.1481	$186.15	$186.15	$186.10
Purchase #7	$153.51	4.329%	$160.1554	$160.16	$160.15	$160.20
7 purchase totals =	$1,006.47		$1,073.4536	$1,073.46	$1,073.50	$1,073.40