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	$144.34	6.115%	$153.1664	$153.17	$153.15	$153.20
Purchase #2	$84.90	11.505%	$94.6677	$94.67	$94.65	$94.70
Purchase #3	$48.39	13.674%	$55.0068	$55.01	$55.00	$55.00
Purchase #4	$31.59	3.572%	$32.7184	$32.72	$32.70	$32.70
Purchase #5	$172.68	13.808%	$196.5237	$196.52	$196.50	$196.50
Purchase #6	$37.69	10.176%	$41.5253	$41.53	$41.55	$41.50
Purchase #7	$163.91	10.712%	$181.468	$181.47	$181.45	$181.50
7 purchase totals =	$683.50		$755.0763	$755.09	$755.00	$755.10