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	$89.35	6.261%	$94.9442	$94.94	$94.95	$94.90
Purchase #2	$224.45	13.375%	$254.4702	$254.47	$254.45	$254.50
Purchase #3	$96.78	10.438%	$106.8819	$106.88	$106.90	$106.90
Purchase #4	$157.37	6.783%	$168.0444	$168.04	$168.05	$168.00
Purchase #5	$240.81	4.506%	$251.6609	$251.66	$251.65	$251.70
Purchase #6	$74.28	6.846%	$79.3652	$79.37	$79.35	$79.40
Purchase #7	$121.73	7.867%	$131.3065	$131.31	$131.30	$131.30
7 purchase totals =	$1,004.77		$1,086.6733	$1,086.67	$1,086.65	$1,086.70