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	$179.46	6.528%	$191.1751	$191.18	$191.20	$191.20
Purchase #2	$203.97	13.539%	$231.5855	$231.59	$231.60	$231.60
Purchase #3	$39.76	13.547%	$45.1463	$45.15	$45.15	$45.10
Purchase #4	$238.84	9.162%	$260.7225	$260.72	$260.70	$260.70
Purchase #5	$58.84	13.173%	$66.591	$66.59	$66.60	$66.60
Purchase #6	$250.92	4.219%	$261.5063	$261.51	$261.50	$261.50
Purchase #7	$182.76	8.617%	$198.5084	$198.51	$198.50	$198.50
7 purchase totals =	$1,154.55		$1,255.2351	$1,255.25	$1,255.25	$1,255.20