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	$240.61	9.248%	$262.8616	$262.86	$262.85	$262.90
Purchase #2	$16.27	11.618%	$18.1602	$18.16	$18.15	$18.20
Purchase #3	$143.75	8.853%	$156.4762	$156.48	$156.50	$156.50
Purchase #4	$22.88	7.388%	$24.5704	$24.57	$24.55	$24.60
Purchase #5	$10.30	8.865%	$11.2131	$11.21	$11.20	$11.20
Purchase #6	$172.73	7.319%	$185.3721	$185.37	$185.35	$185.40
Purchase #7	$106.48	4.398%	$111.163	$111.16	$111.15	$111.20
7 purchase totals =	$713.02		$769.8166	$769.81	$769.75	$770.00