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	$235.74	5.256%	$248.1305	$248.13	$248.15	$248.10
Purchase #2	$182.77	11.804%	$204.3442	$204.34	$204.35	$204.30
Purchase #3	$162.57	5.560%	$171.6089	$171.61	$171.60	$171.60
Purchase #4	$159.50	6.751%	$170.2678	$170.27	$170.25	$170.30
Purchase #5	$87.38	8.802%	$95.0712	$95.07	$95.05	$95.10
Purchase #6	$136.50	5.225%	$143.6321	$143.63	$143.65	$143.60
Purchase #7	$85.27	5.761%	$90.1824	$90.18	$90.20	$90.20
7 purchase totals =	$1,049.73		$1,123.2371	$1,123.23	$1,123.25	$1,123.20