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	$211.45	6.632%	$225.4734	$225.47	$225.45	$225.50
Purchase #2	$243.89	4.597%	$255.1016	$255.10	$255.10	$255.10
Purchase #3	$243.40	11.219%	$270.707	$270.71	$270.70	$270.70
Purchase #4	$11.33	12.430%	$12.7383	$12.74	$12.75	$12.70
Purchase #5	$215.40	3.532%	$223.0079	$223.01	$223.00	$223.00
Purchase #6	$165.52	4.801%	$173.4666	$173.47	$173.45	$173.50
Purchase #7	$37.63	5.747%	$39.7926	$39.79	$39.80	$39.80
7 purchase totals =	$1,128.62		$1,200.2874	$1,200.29	$1,200.25	$1,200.30