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	$230.64	6.182%	$244.8982	$244.90	$244.90	$244.90
Purchase #2	$124.97	9.171%	$136.431	$136.43	$136.45	$136.40
Purchase #3	$145.92	10.110%	$160.6725	$160.67	$160.65	$160.70
Purchase #4	$196.47	13.446%	$222.8874	$222.89	$222.90	$222.90
Purchase #5	$35.68	3.825%	$37.0448	$37.04	$37.05	$37.00
Purchase #6	$36.31	12.690%	$40.9177	$40.92	$40.90	$40.90
Purchase #7	$196.29	8.774%	$213.5125	$213.51	$213.50	$213.50
7 purchase totals =	$966.28		$1,056.3641	$1,056.36	$1,056.35	$1,056.30