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	$82.59	10.815%	$91.5221	$91.52	$91.50	$91.50
Purchase #2	$230.41	7.497%	$247.6838	$247.68	$247.70	$247.70
Purchase #3	$150.33	10.165%	$165.611	$165.61	$165.60	$165.60
Purchase #4	$11.60	4.430%	$12.1139	$12.11	$12.10	$12.10
Purchase #5	$53.53	11.468%	$59.6688	$59.67	$59.65	$59.70
Purchase #6	$65.61	11.249%	$72.9905	$72.99	$73.00	$73.00
Purchase #7	$198.70	6.156%	$210.932	$210.93	$210.95	$210.90
7 purchase totals =	$792.77		$860.5221	$860.51	$860.50	$860.50