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	$134.63	4.358%	$140.4972	$140.50	$140.50	$140.50
Purchase #2	$193.25	3.234%	$199.4997	$199.50	$199.50	$199.50
Purchase #3	$242.81	8.694%	$263.9199	$263.92	$263.90	$263.90
Purchase #4	$175.73	11.433%	$195.8212	$195.82	$195.80	$195.80
Purchase #5	$50.95	7.185%	$54.6108	$54.61	$54.60	$54.60
Purchase #6	$61.33	12.361%	$68.911	$68.91	$68.90	$68.90
Purchase #7	$82.89	6.466%	$88.2497	$88.25	$88.25	$88.20
7 purchase totals =	$941.59		$1,011.5095	$1,011.51	$1,011.45	$1,011.40