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	$14.37	9.274%	$15.7027	$15.70	$15.70	$15.70
Purchase #2	$67.85	7.327%	$72.8214	$72.82	$72.80	$72.80
Purchase #3	$31.69	4.196%	$33.0197	$33.02	$33.00	$33.00
Purchase #4	$11.38	3.672%	$11.7979	$11.80	$11.80	$11.80
Purchase #5	$114.44	7.765%	$123.3263	$123.33	$123.35	$123.30
Purchase #6	$111.61	13.121%	$126.2543	$126.25	$126.25	$126.30
Purchase #7	$18.57	11.732%	$20.7486	$20.75	$20.75	$20.70
7 purchase totals =	$369.91		$403.6709	$403.67	$403.65	$403.60