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	$232.47	5.774%	$245.8928	$245.89	$245.90	$245.90
Purchase #2	$222.87	10.435%	$246.1265	$246.13	$246.15	$246.10
Purchase #3	$123.57	3.182%	$127.502	$127.50	$127.50	$127.50
Purchase #4	$158.96	3.143%	$163.9561	$163.96	$163.95	$164.00
Purchase #5	$123.62	11.319%	$137.6125	$137.61	$137.60	$137.60
Purchase #6	$242.35	13.523%	$275.123	$275.12	$275.10	$275.10
Purchase #7	$236.92	6.136%	$251.4574	$251.46	$251.45	$251.50
7 purchase totals =	$1,340.76		$1,447.6703	$1,447.67	$1,447.65	$1,447.70