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	$189.55	7.695%	$204.1359	$204.14	$204.15	$204.10
Purchase #2	$45.49	4.377%	$47.4811	$47.48	$47.50	$47.50
Purchase #3	$89.57	10.772%	$99.2185	$99.22	$99.20	$99.20
Purchase #4	$141.26	13.157%	$159.8456	$159.85	$159.85	$159.80
Purchase #5	$141.73	13.813%	$161.3072	$161.31	$161.30	$161.30
Purchase #6	$80.74	11.556%	$90.0703	$90.07	$90.05	$90.10
Purchase #7	$221.83	10.108%	$244.2526	$244.25	$244.25	$244.30
7 purchase totals =	$910.17		$1,006.3112	$1,006.32	$1,006.30	$1,006.30