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	$119.47	6.827%	$127.6262	$127.63	$127.65	$127.60
Purchase #2	$57.25	3.492%	$59.2492	$59.25	$59.25	$59.20
Purchase #3	$56.93	12.456%	$64.0212	$64.02	$64.00	$64.00
Purchase #4	$93.72	6.157%	$99.4903	$99.49	$99.50	$99.50
Purchase #5	$48.67	10.219%	$53.6436	$53.64	$53.65	$53.60
Purchase #6	$141.47	5.628%	$149.4319	$149.43	$149.45	$149.40
Purchase #7	$40.65	11.344%	$45.2613	$45.26	$45.25	$45.30
7 purchase totals =	$558.16		$598.7237	$598.72	$598.75	$598.60