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	$155.96	3.275%	$161.0677	$161.07	$161.05	$161.10
Purchase #2	$133.56	4.598%	$139.7011	$139.70	$139.70	$139.70
Purchase #3	$237.58	11.196%	$264.1795	$264.18	$264.20	$264.20
Purchase #4	$89.48	10.853%	$99.1913	$99.19	$99.20	$99.20
Purchase #5	$56.34	10.770%	$62.4078	$62.41	$62.40	$62.40
Purchase #6	$109.30	8.469%	$118.5566	$118.56	$118.55	$118.60
Purchase #7	$186.28	12.656%	$209.8556	$209.86	$209.85	$209.90
7 purchase totals =	$968.50		$1,054.9596	$1,054.97	$1,054.95	$1,055.10