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	$213.68	8.375%	$231.5757	$231.58	$231.60	$231.60
Purchase #2	$83.39	7.258%	$89.4424	$89.44	$89.45	$89.40
Purchase #3	$37.77	13.382%	$42.8244	$42.82	$42.80	$42.80
Purchase #4	$122.62	7.530%	$131.8533	$131.85	$131.85	$131.90
Purchase #5	$109.30	3.341%	$112.9517	$112.95	$112.95	$113.00
Purchase #6	$129.91	8.192%	$140.5522	$140.55	$140.55	$140.60
Purchase #7	$213.83	8.191%	$231.3448	$231.34	$231.35	$231.30
7 purchase totals =	$910.50		$980.5445	$980.53	$980.55	$980.60