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	$141.32	3.262%	$145.9299	$145.93	$145.95	$145.90
Purchase #2	$203.70	6.633%	$217.2114	$217.21	$217.20	$217.20
Purchase #3	$72.98	12.720%	$82.2631	$82.26	$82.25	$82.30
Purchase #4	$165.55	4.263%	$172.6074	$172.61	$172.60	$172.60
Purchase #5	$134.35	11.362%	$149.6148	$149.61	$149.60	$149.60
Purchase #6	$223.47	11.152%	$248.3914	$248.39	$248.40	$248.40
Purchase #7	$26.63	3.250%	$27.4955	$27.50	$27.50	$27.50
7 purchase totals =	$968.00		$1,043.5135	$1,043.51	$1,043.50	$1,043.50