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	$12.42	6.632%	$13.2437	$13.24	$13.25	$13.20
Purchase #2	$7.58	4.663%	$7.9335	$7.93	$7.95	$7.90
Purchase #3	$140.95	12.730%	$158.8929	$158.89	$158.90	$158.90
Purchase #4	$33.82	11.597%	$37.7421	$37.74	$37.75	$37.70
Purchase #5	$165.29	6.177%	$175.5	$175.50	$175.50	$175.50
Purchase #6	$215.25	4.695%	$225.356	$225.36	$225.35	$225.40
Purchase #7	$169.49	9.499%	$185.5899	$185.59	$185.60	$185.60
7 purchase totals =	$744.80		$804.2581	$804.25	$804.30	$804.20