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	$62.57	7.302%	$67.1389	$67.14	$67.15	$67.10
Purchase #2	$7.90	12.308%	$8.8723	$8.87	$8.85	$8.90
Purchase #3	$90.98	6.733%	$97.1057	$97.11	$97.10	$97.10
Purchase #4	$98.38	13.176%	$111.3425	$111.34	$111.35	$111.30
Purchase #5	$106.49	13.541%	$120.9098	$120.91	$120.90	$120.90
Purchase #6	$225.67	4.821%	$236.5496	$236.55	$236.55	$236.50
Purchase #7	$92.61	11.234%	$103.0138	$103.01	$103.00	$103.00
7 purchase totals =	$684.60		$744.9326	$744.93	$744.90	$744.80