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	$29.57	10.692%	$32.7316	$32.73	$32.75	$32.70
Purchase #2	$79.71	3.184%	$82.248	$82.25	$82.25	$82.20
Purchase #3	$155.56	10.780%	$172.3294	$172.33	$172.35	$172.30
Purchase #4	$112.78	6.286%	$119.8694	$119.87	$119.85	$119.90
Purchase #5	$32.37	4.644%	$33.8733	$33.87	$33.85	$33.90
Purchase #6	$227.50	10.446%	$251.2647	$251.26	$251.25	$251.30
Purchase #7	$184.82	3.696%	$191.6509	$191.65	$191.65	$191.70
7 purchase totals =	$822.31		$883.9673	$883.96	$883.95	$884.00