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	$209.93	6.116%	$222.7693	$222.77	$222.75	$222.80
Purchase #2	$216.61	11.666%	$241.8797	$241.88	$241.90	$241.90
Purchase #3	$28.65	10.465%	$31.6482	$31.65	$31.65	$31.60
Purchase #4	$46.99	7.700%	$50.6082	$50.61	$50.60	$50.60
Purchase #5	$105.84	6.286%	$112.4931	$112.49	$112.50	$112.50
Purchase #6	$212.89	13.291%	$241.1852	$241.19	$241.20	$241.20
Purchase #7	$141.71	5.694%	$149.779	$149.78	$149.80	$149.80
7 purchase totals =	$962.62		$1,050.3627	$1,050.37	$1,050.40	$1,050.40