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	$200.89	12.616%	$226.2343	$226.23	$226.25	$226.20
Purchase #2	$168.62	4.123%	$175.5722	$175.57	$175.55	$175.60
Purchase #3	$124.90	10.345%	$137.8209	$137.82	$137.80	$137.80
Purchase #4	$43.92	6.105%	$46.6013	$46.60	$46.60	$46.60
Purchase #5	$10.79	6.159%	$11.4546	$11.45	$11.45	$11.50
Purchase #6	$159.91	3.466%	$165.4525	$165.45	$165.45	$165.50
Purchase #7	$115.69	13.692%	$131.5303	$131.53	$131.55	$131.50
7 purchase totals =	$824.72		$894.6661	$894.65	$894.65	$894.70