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	$159.61	5.464%	$168.3311	$168.33	$168.35	$168.30
Purchase #2	$89.81	7.600%	$96.6356	$96.64	$96.65	$96.60
Purchase #3	$172.35	4.660%	$180.3815	$180.38	$180.40	$180.40
Purchase #4	$59.86	4.129%	$62.3316	$62.33	$62.35	$62.30
Purchase #5	$154.49	13.302%	$175.0403	$175.04	$175.05	$175.00
Purchase #6	$125.62	10.733%	$139.1028	$139.10	$139.10	$139.10
Purchase #7	$165.79	5.503%	$174.9134	$174.91	$174.90	$174.90
7 purchase totals =	$927.53		$996.7363	$996.73	$996.80	$996.60