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	$113.72	12.312%	$127.7212	$127.72	$127.70	$127.70
Purchase #2	$238.86	10.257%	$263.3599	$263.36	$263.35	$263.40
Purchase #3	$248.52	4.745%	$260.3123	$260.31	$260.30	$260.30
Purchase #4	$68.60	11.456%	$76.4588	$76.46	$76.45	$76.50
Purchase #5	$53.87	6.784%	$57.5245	$57.52	$57.50	$57.50
Purchase #6	$182.44	13.234%	$206.5841	$206.58	$206.60	$206.60
Purchase #7	$95.59	7.258%	$102.5279	$102.53	$102.55	$102.50
7 purchase totals =	$1,001.60		$1,094.4887	$1,094.48	$1,094.45	$1,094.50