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	$95.34	4.796%	$99.9125	$99.91	$99.90	$99.90
Purchase #2	$223.58	9.321%	$244.4199	$244.42	$244.40	$244.40
Purchase #3	$70.51	10.513%	$77.9227	$77.92	$77.90	$77.90
Purchase #4	$182.59	9.387%	$199.7297	$199.73	$199.75	$199.70
Purchase #5	$186.86	11.515%	$208.3769	$208.38	$208.40	$208.40
Purchase #6	$56.67	5.195%	$59.614	$59.61	$59.60	$59.60
Purchase #7	$183.40	13.687%	$208.502	$208.50	$208.50	$208.50
7 purchase totals =	$998.95		$1,098.4777	$1,098.47	$1,098.45	$1,098.40