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	$244.56	4.843%	$256.404	$256.40	$256.40	$256.40
Purchase #2	$179.89	12.681%	$202.7019	$202.70	$202.70	$202.70
Purchase #3	$150.79	9.675%	$165.3789	$165.38	$165.40	$165.40
Purchase #4	$22.39	10.626%	$24.7692	$24.77	$24.75	$24.80
Purchase #5	$90.34	10.580%	$99.898	$99.90	$99.90	$99.90
Purchase #6	$244.72	4.824%	$256.5253	$256.53	$256.55	$256.50
Purchase #7	$153.29	13.436%	$173.886	$173.89	$173.90	$173.90
7 purchase totals =	$1,085.98		$1,179.5633	$1,179.57	$1,179.60	$1,179.60