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	$240.83	4.767%	$252.3104	$252.31	$252.30	$252.30
Purchase #2	$71.74	6.805%	$76.6219	$76.62	$76.60	$76.60
Purchase #3	$247.57	7.285%	$265.6055	$265.61	$265.60	$265.60
Purchase #4	$142.55	3.268%	$147.2085	$147.21	$147.20	$147.20
Purchase #5	$143.85	6.239%	$152.8248	$152.82	$152.80	$152.80
Purchase #6	$87.77	4.244%	$91.495	$91.50	$91.50	$91.50
Purchase #7	$64.46	3.766%	$66.8876	$66.89	$66.90	$66.90
7 purchase totals =	$998.77		$1,052.9537	$1,052.96	$1,052.90	$1,052.90