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	$182.42	7.762%	$196.5794	$196.58	$196.60	$196.60
Purchase #2	$225.25	13.215%	$255.0168	$255.02	$255.00	$255.00
Purchase #3	$74.67	3.707%	$77.438	$77.44	$77.45	$77.40
Purchase #4	$18.65	7.787%	$20.1023	$20.10	$20.10	$20.10
Purchase #5	$72.38	3.134%	$74.6484	$74.65	$74.65	$74.60
Purchase #6	$41.81	9.538%	$45.7978	$45.80	$45.80	$45.80
Purchase #7	$181.62	8.421%	$196.9142	$196.91	$196.90	$196.90
7 purchase totals =	$796.80		$866.4969	$866.50	$866.50	$866.40