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	$189.40	8.308%	$205.1354	$205.14	$205.15	$205.10
Purchase #2	$47.92	10.130%	$52.7743	$52.77	$52.75	$52.80
Purchase #3	$75.67	10.815%	$83.8537	$83.85	$83.85	$83.90
Purchase #4	$40.78	10.840%	$45.2006	$45.20	$45.20	$45.20
Purchase #5	$178.26	8.399%	$193.2321	$193.23	$193.25	$193.20
Purchase #6	$52.59	8.167%	$56.885	$56.89	$56.90	$56.90
Purchase #7	$172.98	13.520%	$196.3669	$196.37	$196.35	$196.40
7 purchase totals =	$757.60		$833.4480	$833.45	$833.45	$833.50