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	$221.26	4.467%	$231.1437	$231.14	$231.15	$231.10
Purchase #2	$67.26	13.378%	$76.258	$76.26	$76.25	$76.30
Purchase #3	$124.61	9.612%	$136.5875	$136.59	$136.60	$136.60
Purchase #4	$59.33	11.131%	$65.934	$65.93	$65.95	$65.90
Purchase #5	$95.66	13.438%	$108.5148	$108.51	$108.50	$108.50
Purchase #6	$20.52	9.499%	$22.4692	$22.47	$22.45	$22.50
Purchase #7	$240.25	6.354%	$255.5155	$255.52	$255.50	$255.50
7 purchase totals =	$828.89		$896.4227	$896.42	$896.40	$896.40