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	$170.51	12.511%	$191.8425	$191.84	$191.85	$191.80
Purchase #2	$11.95	3.697%	$12.3918	$12.39	$12.40	$12.40
Purchase #3	$173.44	13.283%	$196.478	$196.48	$196.50	$196.50
Purchase #4	$184.46	8.297%	$199.7646	$199.76	$199.75	$199.80
Purchase #5	$91.73	9.863%	$100.7773	$100.78	$100.80	$100.80
Purchase #6	$18.50	3.560%	$19.1586	$19.16	$19.15	$19.20
Purchase #7	$184.84	7.689%	$199.0523	$199.05	$199.05	$199.10
7 purchase totals =	$835.43		$919.4651	$919.46	$919.50	$919.60