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	$232.76	3.829%	$241.6724	$241.67	$241.65	$241.70
Purchase #2	$160.72	7.592%	$172.9219	$172.92	$172.90	$172.90
Purchase #3	$6.68	6.287%	$7.1	$7.10	$7.10	$7.10
Purchase #4	$130.82	5.121%	$137.5193	$137.52	$137.50	$137.50
Purchase #5	$117.25	13.355%	$132.9087	$132.91	$132.90	$132.90
Purchase #6	$81.77	11.725%	$91.3575	$91.36	$91.35	$91.40
Purchase #7	$183.34	9.256%	$200.31	$200.31	$200.30	$200.30
7 purchase totals =	$913.34		$983.7898	$983.79	$983.70	$983.80