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	$214.88	13.288%	$243.4333	$243.43	$243.45	$243.40
Purchase #2	$91.61	9.652%	$100.4522	$100.45	$100.45	$100.50
Purchase #3	$179.59	9.868%	$197.3119	$197.31	$197.30	$197.30
Purchase #4	$18.49	11.782%	$20.6685	$20.67	$20.65	$20.70
Purchase #5	$49.43	4.113%	$51.4631	$51.46	$51.45	$51.50
Purchase #6	$140.57	4.462%	$146.8422	$146.84	$146.85	$146.80
Purchase #7	$67.37	11.223%	$74.9309	$74.93	$74.95	$74.90
7 purchase totals =	$761.94		$835.1021	$835.09	$835.10	$835.10