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	$125.71	12.425%	$141.3295	$141.33	$141.35	$141.30
Purchase #2	$225.63	11.482%	$251.5368	$251.54	$251.55	$251.50
Purchase #3	$142.61	12.800%	$160.8641	$160.86	$160.85	$160.90
Purchase #4	$41.61	9.846%	$45.7069	$45.71	$45.70	$45.70
Purchase #5	$48.43	5.444%	$51.0665	$51.07	$51.05	$51.10
Purchase #6	$199.58	7.689%	$214.9257	$214.93	$214.95	$214.90
Purchase #7	$133.37	6.759%	$142.3845	$142.38	$142.40	$142.40
7 purchase totals =	$916.94		$1,007.8140	$1,007.82	$1,007.85	$1,007.80