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	$116.43	9.112%	$127.0391	$127.04	$127.05	$127.00
Purchase #2	$71.96	7.604%	$77.4318	$77.43	$77.45	$77.40
Purchase #3	$39.61	3.342%	$40.9338	$40.93	$40.95	$40.90
Purchase #4	$228.82	5.673%	$241.801	$241.80	$241.80	$241.80
Purchase #5	$134.56	13.680%	$152.9678	$152.97	$152.95	$153.00
Purchase #6	$232.53	4.214%	$242.3288	$242.33	$242.35	$242.30
Purchase #7	$74.51	5.672%	$78.7362	$78.74	$78.75	$78.70
7 purchase totals =	$898.42		$961.2385	$961.24	$961.30	$961.10