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	$85.82	8.326%	$92.9654	$92.97	$92.95	$93.00
Purchase #2	$92.88	7.311%	$99.6705	$99.67	$99.65	$99.70
Purchase #3	$37.93	7.833%	$40.9011	$40.90	$40.90	$40.90
Purchase #4	$78.60	7.503%	$84.4974	$84.50	$84.50	$84.50
Purchase #5	$212.47	3.343%	$219.5729	$219.57	$219.55	$219.60
Purchase #6	$159.46	13.181%	$180.4784	$180.48	$180.50	$180.50
Purchase #7	$33.92	10.285%	$37.4087	$37.41	$37.40	$37.40
7 purchase totals =	$701.08		$755.4944	$755.50	$755.45	$755.60