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	$190.89	7.326%	$204.8746	$204.87	$204.85	$204.90
Purchase #2	$167.29	3.179%	$172.6081	$172.61	$172.60	$172.60
Purchase #3	$57.99	4.844%	$60.799	$60.80	$60.80	$60.80
Purchase #4	$157.34	4.562%	$164.5179	$164.52	$164.50	$164.50
Purchase #5	$180.29	5.605%	$190.3953	$190.40	$190.40	$190.40
Purchase #6	$222.49	7.777%	$239.793	$239.79	$239.80	$239.80
Purchase #7	$40.52	9.786%	$44.4853	$44.49	$44.50	$44.50
7 purchase totals =	$1,016.81		$1,077.4732	$1,077.48	$1,077.45	$1,077.50