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	$198.36	11.583%	$221.336	$221.34	$221.35	$221.30
Purchase #2	$26.47	12.426%	$29.7592	$29.76	$29.75	$29.80
Purchase #3	$213.34	11.738%	$238.3818	$238.38	$238.40	$238.40
Purchase #4	$151.70	13.683%	$172.4571	$172.46	$172.45	$172.50
Purchase #5	$82.67	3.487%	$85.5527	$85.55	$85.55	$85.60
Purchase #6	$33.93	3.810%	$35.2227	$35.22	$35.20	$35.20
Purchase #7	$174.92	3.230%	$180.5699	$180.57	$180.55	$180.60
7 purchase totals =	$881.39		$963.2794	$963.28	$963.25	$963.40