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	$141.32	9.543%	$154.8062	$154.81	$154.80	$154.80
Purchase #2	$173.71	6.542%	$185.0741	$185.07	$185.05	$185.10
Purchase #3	$50.34	8.105%	$54.4201	$54.42	$54.40	$54.40
Purchase #4	$30.81	5.488%	$32.5009	$32.50	$32.50	$32.50
Purchase #5	$167.85	11.211%	$186.6677	$186.67	$186.65	$186.70
Purchase #6	$10.43	4.148%	$10.8626	$10.86	$10.85	$10.90
Purchase #7	$71.97	8.152%	$77.837	$77.84	$77.85	$77.80
7 purchase totals =	$646.43		$702.1686	$702.17	$702.10	$702.20