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	$92.56	9.284%	$101.1533	$101.15	$101.15	$101.20
Purchase #2	$96.69	13.167%	$109.4212	$109.42	$109.40	$109.40
Purchase #3	$142.55	12.184%	$159.9183	$159.92	$159.90	$159.90
Purchase #4	$177.28	9.396%	$193.9372	$193.94	$193.95	$193.90
Purchase #5	$139.92	11.367%	$155.8247	$155.82	$155.80	$155.80
Purchase #6	$39.82	10.141%	$43.8581	$43.86	$43.85	$43.90
Purchase #7	$32.84	12.733%	$37.0215	$37.02	$37.00	$37.00
7 purchase totals =	$721.66		$801.1343	$801.13	$801.05	$801.10