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	$242.71	9.543%	$265.8718	$265.87	$265.85	$265.90
Purchase #2	$108.46	10.275%	$119.6043	$119.60	$119.60	$119.60
Purchase #3	$181.66	4.365%	$189.5895	$189.59	$189.60	$189.60
Purchase #4	$249.53	13.109%	$282.2409	$282.24	$282.25	$282.20
Purchase #5	$223.57	9.416%	$244.6214	$244.62	$244.60	$244.60
Purchase #6	$248.51	10.303%	$274.114	$274.11	$274.10	$274.10
Purchase #7	$121.46	13.187%	$137.4769	$137.48	$137.50	$137.50
7 purchase totals =	$1,375.90		$1,513.5188	$1,513.51	$1,513.50	$1,513.50