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	$87.40	4.245%	$91.1101	$91.11	$91.10	$91.10
Purchase #2	$135.45	5.727%	$143.2072	$143.21	$143.20	$143.20
Purchase #3	$6.66	7.204%	$7.1398	$7.14	$7.15	$7.10
Purchase #4	$19.87	7.109%	$21.2826	$21.28	$21.30	$21.30
Purchase #5	$165.34	4.351%	$172.5339	$172.53	$172.55	$172.50
Purchase #6	$154.96	6.816%	$165.5221	$165.52	$165.50	$165.50
Purchase #7	$32.71	5.618%	$34.5476	$34.55	$34.55	$34.50
7 purchase totals =	$602.39		$635.3433	$635.34	$635.35	$635.20