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	$117.26	6.536%	$124.9241	$124.92	$124.90	$124.90
Purchase #2	$184.32	5.334%	$194.1516	$194.15	$194.15	$194.20
Purchase #3	$227.41	10.771%	$251.9043	$251.90	$251.90	$251.90
Purchase #4	$163.50	3.120%	$168.6012	$168.60	$168.60	$168.60
Purchase #5	$147.98	13.873%	$168.5093	$168.51	$168.50	$168.50
Purchase #6	$64.92	11.839%	$72.6059	$72.61	$72.60	$72.60
Purchase #7	$28.79	3.426%	$29.7763	$29.78	$29.80	$29.80
7 purchase totals =	$934.18		$1,010.4727	$1,010.47	$1,010.45	$1,010.50