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	$82.48	8.356%	$89.372	$89.37	$89.35	$89.40
Purchase #2	$222.48	3.807%	$230.9498	$230.95	$230.95	$230.90
Purchase #3	$128.67	8.645%	$139.7935	$139.79	$139.80	$139.80
Purchase #4	$47.48	6.252%	$50.4484	$50.45	$50.45	$50.40
Purchase #5	$93.36	6.797%	$99.7057	$99.71	$99.70	$99.70
Purchase #6	$52.57	5.233%	$55.321	$55.32	$55.30	$55.30
Purchase #7	$88.73	7.640%	$95.509	$95.51	$95.50	$95.50
7 purchase totals =	$715.77		$761.0994	$761.10	$761.05	$761.00