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	$149.77	5.226%	$157.597	$157.60	$157.60	$157.60
Purchase #2	$51.60	4.370%	$53.8549	$53.85	$53.85	$53.90
Purchase #3	$30.96	8.582%	$33.617	$33.62	$33.60	$33.60
Purchase #4	$67.77	6.559%	$72.215	$72.22	$72.20	$72.20
Purchase #5	$175.70	13.764%	$199.8833	$199.88	$199.90	$199.90
Purchase #6	$52.53	13.767%	$59.7618	$59.76	$59.75	$59.80
Purchase #7	$143.86	13.682%	$163.5429	$163.54	$163.55	$163.50
7 purchase totals =	$672.19		$740.4719	$740.47	$740.45	$740.50