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	$164.55	13.508%	$186.7774	$186.78	$186.80	$186.80
Purchase #2	$197.36	5.586%	$208.3845	$208.38	$208.40	$208.40
Purchase #3	$157.60	8.457%	$170.9282	$170.93	$170.95	$170.90
Purchase #4	$55.73	11.406%	$62.0866	$62.09	$62.10	$62.10
Purchase #5	$104.61	6.468%	$111.3762	$111.38	$111.40	$111.40
Purchase #6	$55.98	6.108%	$59.3993	$59.40	$59.40	$59.40
Purchase #7	$77.82	6.422%	$82.8176	$82.82	$82.80	$82.80
7 purchase totals =	$813.65		$881.7698	$881.78	$881.85	$881.80