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	$36.34	3.848%	$37.7384	$37.74	$37.75	$37.70
Purchase #2	$37.65	7.563%	$40.4975	$40.50	$40.50	$40.50
Purchase #3	$118.78	6.401%	$126.3831	$126.38	$126.40	$126.40
Purchase #4	$55.61	10.652%	$61.5336	$61.53	$61.55	$61.50
Purchase #5	$210.59	3.355%	$217.6553	$217.66	$217.65	$217.70
Purchase #6	$240.68	13.591%	$273.3908	$273.39	$273.40	$273.40
Purchase #7	$240.53	7.452%	$258.4543	$258.45	$258.45	$258.50
7 purchase totals =	$940.18		$1,015.6530	$1,015.65	$1,015.70	$1,015.70