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	$75.47	13.411%	$85.5913	$85.59	$85.60	$85.60
Purchase #2	$236.55	5.869%	$250.4331	$250.43	$250.45	$250.40
Purchase #3	$191.53	4.658%	$200.4515	$200.45	$200.45	$200.50
Purchase #4	$30.34	3.861%	$31.5114	$31.51	$31.50	$31.50
Purchase #5	$63.25	10.374%	$69.8116	$69.81	$69.80	$69.80
Purchase #6	$200.60	3.244%	$207.1075	$207.11	$207.10	$207.10
Purchase #7	$9.51	13.825%	$10.8248	$10.82	$10.80	$10.80
7 purchase totals =	$807.25		$855.7312	$855.72	$855.70	$855.70