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	$123.31	11.615%	$137.6325	$137.63	$137.65	$137.60
Purchase #2	$213.61	5.425%	$225.1983	$225.20	$225.20	$225.20
Purchase #3	$92.32	11.831%	$103.2424	$103.24	$103.25	$103.20
Purchase #4	$155.59	3.443%	$160.947	$160.95	$160.95	$160.90
Purchase #5	$41.63	10.385%	$45.9533	$45.95	$45.95	$46.00
Purchase #6	$245.57	13.160%	$277.887	$277.89	$277.90	$277.90
Purchase #7	$203.53	11.837%	$227.6218	$227.62	$227.60	$227.60
7 purchase totals =	$1,075.56		$1,178.4823	$1,178.48	$1,178.50	$1,178.40