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	$201.31	10.360%	$222.1657	$222.17	$222.15	$222.20
Purchase #2	$179.46	7.166%	$192.3201	$192.32	$192.30	$192.30
Purchase #3	$203.30	7.568%	$218.6857	$218.69	$218.70	$218.70
Purchase #4	$145.30	3.543%	$150.448	$150.45	$150.45	$150.40
Purchase #5	$77.72	10.535%	$85.9078	$85.91	$85.90	$85.90
Purchase #6	$209.52	8.761%	$227.876	$227.88	$227.90	$227.90
Purchase #7	$230.89	4.826%	$242.0328	$242.03	$242.05	$242.00
7 purchase totals =	$1,247.50		$1,339.4361	$1,339.45	$1,339.45	$1,339.40