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	$60.89	10.274%	$67.1458	$67.15	$67.15	$67.10
Purchase #2	$27.59	13.231%	$31.2404	$31.24	$31.25	$31.20
Purchase #3	$39.56	7.593%	$42.5638	$42.56	$42.55	$42.60
Purchase #4	$87.74	5.434%	$92.5078	$92.51	$92.50	$92.50
Purchase #5	$180.46	5.126%	$189.7104	$189.71	$189.70	$189.70
Purchase #6	$37.95	12.483%	$42.6873	$42.69	$42.70	$42.70
Purchase #7	$45.95	9.174%	$50.1655	$50.17	$50.15	$50.20
7 purchase totals =	$480.14		$516.0210	$516.03	$516.00	$516.00