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	$64.52	3.785%	$66.9621	$66.96	$66.95	$67.00
Purchase #2	$128.38	11.810%	$143.5417	$143.54	$143.55	$143.50
Purchase #3	$52.33	5.376%	$55.1433	$55.14	$55.15	$55.10
Purchase #4	$65.45	8.214%	$70.8261	$70.83	$70.85	$70.80
Purchase #5	$7.36	10.872%	$8.1602	$8.16	$8.15	$8.20
Purchase #6	$125.94	4.603%	$131.737	$131.74	$131.75	$131.70
Purchase #7	$93.70	6.565%	$99.8514	$99.85	$99.85	$99.90
7 purchase totals =	$537.68		$576.2218	$576.22	$576.25	$576.20