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	$133.88	8.842%	$145.7177	$145.72	$145.70	$145.70
Purchase #2	$93.96	6.800%	$100.3493	$100.35	$100.35	$100.30
Purchase #3	$161.45	7.674%	$173.8397	$173.84	$173.85	$173.80
Purchase #4	$101.33	7.166%	$108.5913	$108.59	$108.60	$108.60
Purchase #5	$77.37	4.389%	$80.7658	$80.77	$80.75	$80.80
Purchase #6	$37.58	8.793%	$40.8844	$40.88	$40.90	$40.90
Purchase #7	$217.54	11.294%	$242.109	$242.11	$242.10	$242.10
7 purchase totals =	$823.11		$892.2572	$892.26	$892.25	$892.20