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	$187.47	4.270%	$195.475	$195.48	$195.50	$195.50
Purchase #2	$88.50	12.263%	$99.3528	$99.35	$99.35	$99.40
Purchase #3	$89.58	12.201%	$100.5097	$100.51	$100.50	$100.50
Purchase #4	$150.58	12.471%	$169.3588	$169.36	$169.35	$169.40
Purchase #5	$50.61	8.249%	$54.7848	$54.78	$54.80	$54.80
Purchase #6	$131.60	9.585%	$144.2139	$144.21	$144.20	$144.20
Purchase #7	$38.72	13.728%	$44.0355	$44.04	$44.05	$44.00
7 purchase totals =	$737.06		$807.7305	$807.73	$807.75	$807.80