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	$120.38	8.131%	$130.1681	$130.17	$130.15	$130.20
Purchase #2	$175.33	12.306%	$196.9061	$196.91	$196.90	$196.90
Purchase #3	$245.49	5.698%	$259.478	$259.48	$259.50	$259.50
Purchase #4	$167.97	12.468%	$188.9125	$188.91	$188.90	$188.90
Purchase #5	$152.66	13.363%	$173.06	$173.06	$173.05	$173.10
Purchase #6	$202.54	9.503%	$221.7874	$221.79	$221.80	$221.80
Purchase #7	$206.46	9.259%	$225.5761	$225.58	$225.60	$225.60
7 purchase totals =	$1,270.83		$1,395.8882	$1,395.90	$1,395.90	$1,396.00