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	$140.76	6.370%	$149.7264	$149.73	$149.75	$149.70
Purchase #2	$221.38	13.383%	$251.0073	$251.01	$251.00	$251.00
Purchase #3	$198.29	9.356%	$216.842	$216.84	$216.85	$216.80
Purchase #4	$137.45	10.675%	$152.1228	$152.12	$152.10	$152.10
Purchase #5	$117.38	9.164%	$128.1367	$128.14	$128.15	$128.10
Purchase #6	$67.66	6.663%	$72.1682	$72.17	$72.15	$72.20
Purchase #7	$131.60	6.770%	$140.5093	$140.51	$140.50	$140.50
7 purchase totals =	$1,014.52		$1,110.5127	$1,110.52	$1,110.50	$1,110.40