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	$32.75	12.774%	$36.9335	$36.93	$36.95	$36.90
Purchase #2	$225.64	9.495%	$247.0645	$247.06	$247.05	$247.10
Purchase #3	$63.83	4.149%	$66.4783	$66.48	$66.50	$66.50
Purchase #4	$61.58	3.767%	$63.8997	$63.90	$63.90	$63.90
Purchase #5	$37.37	8.120%	$40.4044	$40.40	$40.40	$40.40
Purchase #6	$33.86	11.807%	$37.8579	$37.86	$37.85	$37.90
Purchase #7	$69.70	5.439%	$73.491	$73.49	$73.50	$73.50
7 purchase totals =	$524.73		$566.1293	$566.12	$566.15	$566.20