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	$31.72	5.451%	$33.4491	$33.45	$33.45	$33.40
Purchase #2	$139.42	5.329%	$146.8497	$146.85	$146.85	$146.80
Purchase #3	$109.30	9.699%	$119.901	$119.90	$119.90	$119.90
Purchase #4	$222.45	6.486%	$236.8781	$236.88	$236.90	$236.90
Purchase #5	$228.87	6.124%	$242.886	$242.89	$242.90	$242.90
Purchase #6	$243.30	3.412%	$251.6014	$251.60	$251.60	$251.60
Purchase #7	$48.99	13.721%	$55.7119	$55.71	$55.70	$55.70
7 purchase totals =	$1,024.05		$1,087.2772	$1,087.28	$1,087.30	$1,087.20