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	$66.73	6.649%	$71.1669	$71.17	$71.15	$71.20
Purchase #2	$106.50	10.181%	$117.3428	$117.34	$117.35	$117.30
Purchase #3	$168.66	9.247%	$184.256	$184.26	$184.25	$184.30
Purchase #4	$203.48	10.500%	$224.8454	$224.85	$224.85	$224.80
Purchase #5	$105.30	12.291%	$118.2424	$118.24	$118.25	$118.20
Purchase #6	$217.55	13.131%	$246.1165	$246.12	$246.10	$246.10
Purchase #7	$38.48	4.405%	$40.175	$40.18	$40.20	$40.20
7 purchase totals =	$906.70		$1,002.1450	$1,002.16	$1,002.15	$1,002.10