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	$10.28	8.253%	$11.1284	$11.13	$11.15	$11.10
Purchase #2	$158.93	13.314%	$180.0899	$180.09	$180.10	$180.10
Purchase #3	$150.42	6.519%	$160.2259	$160.23	$160.25	$160.20
Purchase #4	$25.55	7.439%	$27.4507	$27.45	$27.45	$27.50
Purchase #5	$155.35	11.687%	$173.5058	$173.51	$173.50	$173.50
Purchase #6	$209.86	13.224%	$237.6119	$237.61	$237.60	$237.60
Purchase #7	$82.27	3.731%	$85.3395	$85.34	$85.35	$85.30
7 purchase totals =	$792.66		$875.3521	$875.36	$875.40	$875.30