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	$232.60	6.131%	$246.8607	$246.86	$246.85	$246.90
Purchase #2	$242.47	3.555%	$251.0898	$251.09	$251.10	$251.10
Purchase #3	$203.70	4.685%	$213.2433	$213.24	$213.25	$213.20
Purchase #4	$244.56	12.506%	$275.1447	$275.14	$275.15	$275.10
Purchase #5	$101.71	9.389%	$111.2596	$111.26	$111.25	$111.30
Purchase #6	$95.43	4.294%	$99.5278	$99.53	$99.55	$99.50
Purchase #7	$188.38	7.661%	$202.8118	$202.81	$202.80	$202.80
7 purchase totals =	$1,308.85		$1,399.9377	$1,399.93	$1,399.95	$1,399.90