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	$167.62	10.471%	$185.1715	$185.17	$185.15	$185.20
Purchase #2	$85.78	3.152%	$88.4838	$88.48	$88.50	$88.50
Purchase #3	$101.98	3.652%	$105.7043	$105.70	$105.70	$105.70
Purchase #4	$228.67	3.196%	$235.9783	$235.98	$236.00	$236.00
Purchase #5	$151.84	13.421%	$172.2184	$172.22	$172.20	$172.20
Purchase #6	$246.47	3.806%	$255.8506	$255.85	$255.85	$255.90
Purchase #7	$37.95	13.187%	$42.9545	$42.95	$42.95	$43.00
7 purchase totals =	$1,020.31		$1,086.3614	$1,086.35	$1,086.35	$1,086.50