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	$147.58	13.306%	$167.217	$167.22	$167.20	$167.20
Purchase #2	$207.25	8.631%	$225.1377	$225.14	$225.15	$225.10
Purchase #3	$230.65	6.261%	$245.091	$245.09	$245.10	$245.10
Purchase #4	$77.69	6.663%	$82.8665	$82.87	$82.85	$82.90
Purchase #5	$59.57	4.424%	$62.2054	$62.21	$62.20	$62.20
Purchase #6	$198.96	8.185%	$215.2449	$215.24	$215.25	$215.20
Purchase #7	$230.68	10.742%	$255.4596	$255.46	$255.45	$255.50
7 purchase totals =	$1,152.38		$1,253.2221	$1,253.23	$1,253.20	$1,253.20