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	$57.57	13.489%	$65.3356	$65.34	$65.35	$65.30
Purchase #2	$44.86	11.130%	$49.8529	$49.85	$49.85	$49.90
Purchase #3	$157.73	9.190%	$172.2254	$172.23	$172.25	$172.20
Purchase #4	$220.41	5.836%	$233.2731	$233.27	$233.25	$233.30
Purchase #5	$218.29	11.531%	$243.461	$243.46	$243.45	$243.50
Purchase #6	$135.71	5.527%	$143.2107	$143.21	$143.20	$143.20
Purchase #7	$248.79	13.131%	$281.4586	$281.46	$281.45	$281.50
7 purchase totals =	$1,083.36		$1,188.8173	$1,188.82	$1,188.80	$1,188.90