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	$32.67	3.478%	$33.8063	$33.81	$33.80	$33.80
Purchase #2	$168.32	8.403%	$182.4639	$182.46	$182.45	$182.50
Purchase #3	$21.31	12.688%	$24.0138	$24.01	$24.00	$24.00
Purchase #4	$85.60	6.805%	$91.4251	$91.43	$91.45	$91.40
Purchase #5	$125.50	11.789%	$140.2952	$140.30	$140.30	$140.30
Purchase #6	$111.69	6.813%	$119.2994	$119.30	$119.30	$119.30
Purchase #7	$88.78	4.256%	$92.5585	$92.56	$92.55	$92.60
7 purchase totals =	$633.87		$683.8622	$683.87	$683.85	$683.90