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	$124.41	5.733%	$131.5424	$131.54	$131.55	$131.50
Purchase #2	$216.91	7.532%	$233.2477	$233.25	$233.25	$233.20
Purchase #3	$246.64	4.661%	$258.1359	$258.14	$258.15	$258.10
Purchase #4	$13.47	13.596%	$15.3014	$15.30	$15.30	$15.30
Purchase #5	$133.51	9.593%	$146.3176	$146.32	$146.30	$146.30
Purchase #6	$170.27	5.634%	$179.863	$179.86	$179.85	$179.90
Purchase #7	$157.46	3.609%	$163.1427	$163.14	$163.15	$163.10
7 purchase totals =	$1,062.67		$1,127.5507	$1,127.55	$1,127.55	$1,127.40