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	$118.56	7.823%	$127.8349	$127.83	$127.85	$127.80
Purchase #2	$189.70	12.457%	$213.3309	$213.33	$213.35	$213.30
Purchase #3	$130.33	12.549%	$146.6851	$146.69	$146.70	$146.70
Purchase #4	$53.60	8.148%	$57.9673	$57.97	$57.95	$58.00
Purchase #5	$224.69	11.491%	$250.5091	$250.51	$250.50	$250.50
Purchase #6	$106.52	11.296%	$118.5525	$118.55	$118.55	$118.60
Purchase #7	$64.40	3.803%	$66.8491	$66.85	$66.85	$66.80
7 purchase totals =	$887.80		$981.7289	$981.73	$981.75	$981.70