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	$192.38	12.588%	$216.5968	$216.60	$216.60	$216.60
Purchase #2	$28.50	12.701%	$32.1198	$32.12	$32.10	$32.10
Purchase #3	$247.38	3.577%	$256.2288	$256.23	$256.25	$256.20
Purchase #4	$77.52	9.385%	$84.7953	$84.80	$84.80	$84.80
Purchase #5	$149.45	6.616%	$159.3376	$159.34	$159.35	$159.30
Purchase #6	$59.27	10.561%	$65.5295	$65.53	$65.55	$65.50
Purchase #7	$177.89	12.274%	$199.7242	$199.72	$199.70	$199.70
7 purchase totals =	$932.39		$1,014.3320	$1,014.34	$1,014.35	$1,014.20