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	$178.49	12.331%	$200.4996	$200.50	$200.50	$200.50
Purchase #2	$75.99	13.738%	$86.4295	$86.43	$86.45	$86.40
Purchase #3	$191.42	13.620%	$217.4914	$217.49	$217.50	$217.50
Purchase #4	$105.99	6.747%	$113.1411	$113.14	$113.15	$113.10
Purchase #5	$52.34	3.386%	$54.1122	$54.11	$54.10	$54.10
Purchase #6	$115.89	6.455%	$123.3707	$123.37	$123.35	$123.40
Purchase #7	$235.84	12.336%	$264.9332	$264.93	$264.95	$264.90
7 purchase totals =	$955.96		$1,059.9777	$1,059.97	$1,060.00	$1,059.90