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	$95.48	10.657%	$105.6553	$105.66	$105.65	$105.70
Purchase #2	$202.93	12.232%	$227.7524	$227.75	$227.75	$227.80
Purchase #3	$141.83	4.872%	$148.74	$148.74	$148.75	$148.70
Purchase #4	$99.94	9.396%	$109.3304	$109.33	$109.35	$109.30
Purchase #5	$57.40	4.388%	$59.9187	$59.92	$59.90	$59.90
Purchase #6	$146.66	3.129%	$151.249	$151.25	$151.25	$151.20
Purchase #7	$35.73	9.731%	$39.2069	$39.21	$39.20	$39.20
7 purchase totals =	$779.97		$841.8527	$841.86	$841.85	$841.80