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	$43.34	4.625%	$45.3445	$45.34	$45.35	$45.30
Purchase #2	$89.81	12.375%	$100.924	$100.92	$100.90	$100.90
Purchase #3	$74.61	9.135%	$81.4256	$81.43	$81.45	$81.40
Purchase #4	$139.42	5.194%	$146.6615	$146.66	$146.65	$146.70
Purchase #5	$61.28	6.589%	$65.3177	$65.32	$65.30	$65.30
Purchase #6	$243.54	12.334%	$273.5782	$273.58	$273.60	$273.60
Purchase #7	$216.69	6.656%	$231.1129	$231.11	$231.10	$231.10
7 purchase totals =	$868.69		$944.3644	$944.36	$944.35	$944.30