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	$225.25	5.476%	$237.5847	$237.58	$237.60	$237.60
Purchase #2	$125.95	4.428%	$131.5271	$131.53	$131.55	$131.50
Purchase #3	$174.71	9.559%	$191.4105	$191.41	$191.40	$191.40
Purchase #4	$40.79	3.344%	$42.154	$42.15	$42.15	$42.20
Purchase #5	$232.96	11.505%	$259.762	$259.76	$259.75	$259.80
Purchase #6	$205.51	6.866%	$219.6203	$219.62	$219.60	$219.60
Purchase #7	$103.89	7.289%	$111.4625	$111.46	$111.45	$111.50
7 purchase totals =	$1,109.06		$1,193.5211	$1,193.51	$1,193.50	$1,193.60