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	$166.47	5.400%	$175.4594	$175.46	$175.45	$175.50
Purchase #2	$55.44	4.866%	$58.1377	$58.14	$58.15	$58.10
Purchase #3	$226.77	12.515%	$255.1503	$255.15	$255.15	$255.20
Purchase #4	$41.61	5.546%	$43.9177	$43.92	$43.90	$43.90
Purchase #5	$138.70	6.795%	$148.1247	$148.12	$148.10	$148.10
Purchase #6	$71.91	9.663%	$78.8587	$78.86	$78.85	$78.90
Purchase #7	$151.30	3.311%	$156.3095	$156.31	$156.30	$156.30
7 purchase totals =	$852.20		$915.9580	$915.96	$915.90	$916.00