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	$6.28	11.720%	$7.016	$7.02	$7.00	$7.00
Purchase #2	$144.94	4.201%	$151.0289	$151.03	$151.05	$151.00
Purchase #3	$186.80	5.161%	$196.4407	$196.44	$196.45	$196.40
Purchase #4	$93.34	8.308%	$101.0947	$101.09	$101.10	$101.10
Purchase #5	$89.88	13.787%	$102.2718	$102.27	$102.25	$102.30
Purchase #6	$241.80	5.232%	$254.451	$254.45	$254.45	$254.50
Purchase #7	$127.53	7.487%	$137.0782	$137.08	$137.10	$137.10
7 purchase totals =	$890.57		$949.3813	$949.38	$949.40	$949.40