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	$105.55	8.582%	$114.6083	$114.61	$114.60	$114.60
Purchase #2	$76.72	8.466%	$83.2151	$83.22	$83.20	$83.20
Purchase #3	$18.49	4.285%	$19.2823	$19.28	$19.30	$19.30
Purchase #4	$219.79	5.770%	$232.4719	$232.47	$232.45	$232.50
Purchase #5	$76.30	8.467%	$82.7603	$82.76	$82.75	$82.80
Purchase #6	$63.53	6.425%	$67.6118	$67.61	$67.60	$67.60
Purchase #7	$123.51	12.394%	$138.8178	$138.82	$138.80	$138.80
7 purchase totals =	$683.89		$738.7675	$738.77	$738.70	$738.80