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	$82.50	7.416%	$88.6182	$88.62	$88.60	$88.60
Purchase #2	$173.75	10.778%	$192.4768	$192.48	$192.50	$192.50
Purchase #3	$64.98	11.603%	$72.5196	$72.52	$72.50	$72.50
Purchase #4	$228.94	8.707%	$248.8738	$248.87	$248.85	$248.90
Purchase #5	$159.91	11.699%	$178.6179	$178.62	$178.60	$178.60
Purchase #6	$34.58	8.135%	$37.3931	$37.39	$37.40	$37.40
Purchase #7	$141.74	6.508%	$150.9644	$150.96	$150.95	$151.00
7 purchase totals =	$886.40		$969.4638	$969.46	$969.40	$969.50