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	$89.76	5.479%	$94.678	$94.68	$94.70	$94.70
Purchase #2	$209.54	10.457%	$231.4516	$231.45	$231.45	$231.50
Purchase #3	$80.28	11.226%	$89.2922	$89.29	$89.30	$89.30
Purchase #4	$185.26	8.149%	$200.3568	$200.36	$200.35	$200.40
Purchase #5	$205.89	13.685%	$234.066	$234.07	$234.05	$234.10
Purchase #6	$73.89	6.444%	$78.6515	$78.65	$78.65	$78.70
Purchase #7	$34.32	7.780%	$36.9901	$36.99	$37.00	$37.00
7 purchase totals =	$878.94		$965.4862	$965.49	$965.50	$965.70