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	$161.88	6.606%	$172.5738	$172.57	$172.55	$172.60
Purchase #2	$158.29	8.351%	$171.5088	$171.51	$171.50	$171.50
Purchase #3	$150.58	13.825%	$171.3977	$171.40	$171.40	$171.40
Purchase #4	$116.66	8.580%	$126.6694	$126.67	$126.65	$126.70
Purchase #5	$148.48	13.574%	$168.6347	$168.63	$168.65	$168.60
Purchase #6	$213.51	6.590%	$227.5803	$227.58	$227.60	$227.60
Purchase #7	$10.82	9.512%	$11.8492	$11.85	$11.85	$11.80
7 purchase totals =	$960.22		$1,050.2139	$1,050.21	$1,050.20	$1,050.20