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	$174.90	8.332%	$189.4727	$189.47	$189.45	$189.50
Purchase #2	$221.86	13.155%	$251.0457	$251.05	$251.05	$251.00
Purchase #3	$43.89	9.615%	$48.11	$48.11	$48.10	$48.10
Purchase #4	$28.66	8.861%	$31.1996	$31.20	$31.20	$31.20
Purchase #5	$32.78	13.790%	$37.3004	$37.30	$37.30	$37.30
Purchase #6	$119.48	9.842%	$131.2392	$131.24	$131.25	$131.20
Purchase #7	$148.89	11.561%	$166.1032	$166.10	$166.10	$166.10
7 purchase totals =	$770.46		$854.4708	$854.47	$854.45	$854.40