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	$185.45	13.321%	$210.1538	$210.15	$210.15	$210.20
Purchase #2	$84.40	5.457%	$89.0057	$89.01	$89.00	$89.00
Purchase #3	$123.65	11.192%	$137.4889	$137.49	$137.50	$137.50
Purchase #4	$33.28	13.330%	$37.7162	$37.72	$37.70	$37.70
Purchase #5	$146.74	9.740%	$161.0325	$161.03	$161.05	$161.00
Purchase #6	$212.26	9.182%	$231.7497	$231.75	$231.75	$231.70
Purchase #7	$206.71	12.113%	$231.7488	$231.75	$231.75	$231.70
7 purchase totals =	$992.49		$1,098.8956	$1,098.90	$1,098.90	$1,098.80