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	$172.29	11.302%	$191.7622	$191.76	$191.75	$191.80
Purchase #2	$140.48	10.642%	$155.4299	$155.43	$155.45	$155.40
Purchase #3	$128.63	4.801%	$134.8055	$134.81	$134.80	$134.80
Purchase #4	$106.41	5.309%	$112.0593	$112.06	$112.05	$112.10
Purchase #5	$147.81	11.592%	$164.9441	$164.94	$164.95	$164.90
Purchase #6	$147.27	8.320%	$159.5229	$159.52	$159.50	$159.50
Purchase #7	$50.65	11.576%	$56.5132	$56.51	$56.50	$56.50
7 purchase totals =	$893.54		$975.0371	$975.03	$975.00	$975.00