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	$130.72	10.362%	$144.2652	$144.27	$144.25	$144.30
Purchase #2	$69.69	11.765%	$77.889	$77.89	$77.90	$77.90
Purchase #3	$11.54	9.583%	$12.6459	$12.65	$12.65	$12.60
Purchase #4	$207.54	7.698%	$223.5164	$223.52	$223.50	$223.50
Purchase #5	$169.89	11.218%	$188.9483	$188.95	$188.95	$188.90
Purchase #6	$144.54	8.769%	$157.2147	$157.21	$157.20	$157.20
Purchase #7	$150.25	7.426%	$161.4076	$161.41	$161.40	$161.40
7 purchase totals =	$884.17		$965.8871	$965.90	$965.85	$965.80