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	$88.84	11.698%	$99.2325	$99.23	$99.25	$99.20
Purchase #2	$213.81	6.262%	$227.1988	$227.20	$227.20	$227.20
Purchase #3	$12.55	4.437%	$13.1068	$13.11	$13.10	$13.10
Purchase #4	$165.88	6.616%	$176.8546	$176.85	$176.85	$176.90
Purchase #5	$150.36	5.530%	$158.6749	$158.67	$158.65	$158.70
Purchase #6	$206.25	9.168%	$225.159	$225.16	$225.15	$225.20
Purchase #7	$164.36	12.872%	$185.5164	$185.52	$185.50	$185.50
7 purchase totals =	$1,002.05		$1,085.7430	$1,085.74	$1,085.70	$1,085.80