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	$87.75	9.274%	$95.8879	$95.89	$95.90	$95.90
Purchase #2	$181.78	11.685%	$203.021	$203.02	$203.00	$203.00
Purchase #3	$142.91	3.825%	$148.3763	$148.38	$148.40	$148.40
Purchase #4	$16.76	10.169%	$18.4643	$18.46	$18.45	$18.50
Purchase #5	$89.37	13.815%	$101.7165	$101.72	$101.70	$101.70
Purchase #6	$82.86	13.401%	$93.9641	$93.96	$93.95	$94.00
Purchase #7	$160.28	8.222%	$173.4582	$173.46	$173.45	$173.50
7 purchase totals =	$761.71		$834.8883	$834.89	$834.85	$835.00