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	$51.76	4.209%	$53.9386	$53.94	$53.95	$53.90
Purchase #2	$248.79	4.390%	$259.7119	$259.71	$259.70	$259.70
Purchase #3	$108.86	13.598%	$123.6628	$123.66	$123.65	$123.70
Purchase #4	$189.30	10.592%	$209.3507	$209.35	$209.35	$209.40
Purchase #5	$87.78	13.205%	$99.3713	$99.37	$99.35	$99.40
Purchase #6	$74.87	11.126%	$83.2	$83.20	$83.20	$83.20
Purchase #7	$216.30	12.297%	$242.8984	$242.90	$242.90	$242.90
7 purchase totals =	$977.66		$1,072.1337	$1,072.13	$1,072.10	$1,072.20