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	$210.98	9.774%	$231.6012	$231.60	$231.60	$231.60
Purchase #2	$131.60	9.102%	$143.5782	$143.58	$143.60	$143.60
Purchase #3	$79.66	10.720%	$88.1996	$88.20	$88.20	$88.20
Purchase #4	$158.32	9.196%	$172.8791	$172.88	$172.90	$172.90
Purchase #5	$178.34	7.460%	$191.6442	$191.64	$191.65	$191.60
Purchase #6	$117.64	11.106%	$130.7051	$130.71	$130.70	$130.70
Purchase #7	$192.70	11.853%	$215.5407	$215.54	$215.55	$215.50
7 purchase totals =	$1,069.24		$1,174.1481	$1,174.15	$1,174.20	$1,174.10