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	$241.90	12.373%	$271.8303	$271.83	$271.85	$271.80
Purchase #2	$200.44	11.383%	$223.2561	$223.26	$223.25	$223.30
Purchase #3	$137.99	9.196%	$150.6796	$150.68	$150.70	$150.70
Purchase #4	$85.96	5.759%	$90.9104	$90.91	$90.90	$90.90
Purchase #5	$227.80	7.130%	$244.0421	$244.04	$244.05	$244.00
Purchase #6	$141.89	7.479%	$152.502	$152.50	$152.50	$152.50
Purchase #7	$135.95	4.579%	$142.1752	$142.18	$142.20	$142.20
7 purchase totals =	$1,171.93		$1,275.3957	$1,275.40	$1,275.45	$1,275.40