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	$203.84	5.634%	$215.3243	$215.32	$215.30	$215.30
Purchase #2	$14.51	4.476%	$15.1595	$15.16	$15.15	$15.20
Purchase #3	$165.30	12.427%	$185.8418	$185.84	$185.85	$185.80
Purchase #4	$237.89	6.831%	$254.1403	$254.14	$254.15	$254.10
Purchase #5	$237.73	8.526%	$257.9989	$258.00	$258.00	$258.00
Purchase #6	$81.66	12.557%	$91.914	$91.91	$91.90	$91.90
Purchase #7	$51.30	4.204%	$53.4567	$53.46	$53.45	$53.50
7 purchase totals =	$992.23		$1,073.8355	$1,073.83	$1,073.80	$1,073.80