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	$73.88	4.511%	$77.2127	$77.21	$77.20	$77.20
Purchase #2	$23.78	8.495%	$25.8001	$25.80	$25.80	$25.80
Purchase #3	$93.48	13.276%	$105.8904	$105.89	$105.90	$105.90
Purchase #4	$151.79	10.177%	$167.2377	$167.24	$167.25	$167.20
Purchase #5	$211.63	13.729%	$240.6847	$240.68	$240.70	$240.70
Purchase #6	$83.71	7.105%	$89.6576	$89.66	$89.65	$89.70
Purchase #7	$87.40	8.734%	$95.0335	$95.03	$95.05	$95.00
7 purchase totals =	$725.67		$801.5167	$801.51	$801.55	$801.50