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	$174.60	4.621%	$182.6683	$182.67	$182.65	$182.70
Purchase #2	$206.80	12.294%	$232.224	$232.22	$232.20	$232.20
Purchase #3	$41.33	6.329%	$43.9458	$43.95	$43.95	$43.90
Purchase #4	$37.53	8.133%	$40.5823	$40.58	$40.60	$40.60
Purchase #5	$62.44	8.682%	$67.861	$67.86	$67.85	$67.90
Purchase #6	$121.30	7.515%	$130.4157	$130.42	$130.40	$130.40
Purchase #7	$90.43	11.484%	$100.815	$100.82	$100.80	$100.80
7 purchase totals =	$734.43		$798.5121	$798.52	$798.45	$798.50