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	$66.43	8.303%	$71.9457	$71.95	$71.95	$71.90
Purchase #2	$25.46	10.143%	$28.0424	$28.04	$28.05	$28.00
Purchase #3	$62.77	4.251%	$65.4384	$65.44	$65.45	$65.40
Purchase #4	$114.43	4.544%	$119.6297	$119.63	$119.65	$119.60
Purchase #5	$212.57	13.587%	$241.4519	$241.45	$241.45	$241.50
Purchase #6	$147.50	13.147%	$166.8918	$166.89	$166.90	$166.90
Purchase #7	$181.43	13.184%	$205.3497	$205.35	$205.35	$205.30
7 purchase totals =	$810.59		$898.7496	$898.75	$898.80	$898.60