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	$81.48	4.322%	$85.0016	$85.00	$85.00	$85.00
Purchase #2	$76.64	6.372%	$81.5235	$81.52	$81.50	$81.50
Purchase #3	$105.42	3.763%	$109.387	$109.39	$109.40	$109.40
Purchase #4	$86.51	9.111%	$94.3919	$94.39	$94.40	$94.40
Purchase #5	$86.26	6.491%	$91.8591	$91.86	$91.85	$91.90
Purchase #6	$160.66	5.766%	$169.9237	$169.92	$169.90	$169.90
Purchase #7	$227.64	7.284%	$244.2213	$244.22	$244.20	$244.20
7 purchase totals =	$824.61		$876.3081	$876.30	$876.25	$876.30