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	$75.57	13.517%	$85.7848	$85.78	$85.80	$85.80
Purchase #2	$68.89	4.485%	$71.9797	$71.98	$72.00	$72.00
Purchase #3	$90.37	11.209%	$100.4996	$100.50	$100.50	$100.50
Purchase #4	$82.91	12.520%	$93.2903	$93.29	$93.30	$93.30
Purchase #5	$107.87	9.814%	$118.4564	$118.46	$118.45	$118.50
Purchase #6	$50.67	5.500%	$53.4569	$53.46	$53.45	$53.50
Purchase #7	$208.70	6.481%	$222.2258	$222.23	$222.25	$222.20
7 purchase totals =	$684.98		$745.6935	$745.70	$745.75	$745.80