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	$140.54	3.588%	$145.5826	$145.58	$145.60	$145.60
Purchase #2	$134.90	9.319%	$147.4713	$147.47	$147.45	$147.50
Purchase #3	$66.32	8.303%	$71.8265	$71.83	$71.85	$71.80
Purchase #4	$11.48	9.688%	$12.5922	$12.59	$12.60	$12.60
Purchase #5	$180.61	5.104%	$189.8283	$189.83	$189.85	$189.80
Purchase #6	$230.79	12.841%	$260.4257	$260.43	$260.45	$260.40
Purchase #7	$165.93	11.506%	$185.0219	$185.02	$185.00	$185.00
7 purchase totals =	$930.57		$1,012.7485	$1,012.75	$1,012.80	$1,012.70