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	$175.94	8.590%	$191.0532	$191.05	$191.05	$191.10
Purchase #2	$80.27	6.768%	$85.7027	$85.70	$85.70	$85.70
Purchase #3	$132.79	3.754%	$137.7749	$137.77	$137.75	$137.80
Purchase #4	$41.78	9.722%	$45.8419	$45.84	$45.85	$45.80
Purchase #5	$204.85	5.693%	$216.5121	$216.51	$216.50	$216.50
Purchase #6	$205.73	12.486%	$231.4174	$231.42	$231.40	$231.40
Purchase #7	$68.49	13.751%	$77.9081	$77.91	$77.90	$77.90
7 purchase totals =	$909.85		$986.2103	$986.20	$986.15	$986.20