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	$157.52	11.472%	$175.5907	$175.59	$175.60	$175.60
Purchase #2	$67.60	4.675%	$70.7603	$70.76	$70.75	$70.80
Purchase #3	$208.38	9.435%	$228.0407	$228.04	$228.05	$228.00
Purchase #4	$100.32	12.164%	$112.5229	$112.52	$112.50	$112.50
Purchase #5	$109.28	7.209%	$117.158	$117.16	$117.15	$117.20
Purchase #6	$28.90	5.356%	$30.4479	$30.45	$30.45	$30.40
Purchase #7	$181.61	10.366%	$200.4357	$200.44	$200.45	$200.40
7 purchase totals =	$853.61		$934.9562	$934.96	$934.95	$934.90