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	$153.57	8.384%	$166.4453	$166.45	$166.45	$166.40
Purchase #2	$181.26	4.519%	$189.4511	$189.45	$189.45	$189.50
Purchase #3	$195.39	5.390%	$205.9215	$205.92	$205.90	$205.90
Purchase #4	$74.95	13.646%	$85.1777	$85.18	$85.20	$85.20
Purchase #5	$75.70	7.597%	$81.4509	$81.45	$81.45	$81.50
Purchase #6	$66.98	7.515%	$72.0135	$72.01	$72.00	$72.00
Purchase #7	$242.96	12.311%	$272.8708	$272.87	$272.85	$272.90
7 purchase totals =	$990.81		$1,073.3308	$1,073.33	$1,073.30	$1,073.40