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	$31.89	4.564%	$33.3455	$33.35	$33.35	$33.30
Purchase #2	$200.69	5.108%	$210.9412	$210.94	$210.95	$210.90
Purchase #3	$39.32	3.399%	$40.6565	$40.66	$40.65	$40.70
Purchase #4	$197.33	12.468%	$221.9331	$221.93	$221.95	$221.90
Purchase #5	$69.35	4.515%	$72.4812	$72.48	$72.50	$72.50
Purchase #6	$153.86	7.348%	$165.1656	$165.17	$165.15	$165.20
Purchase #7	$114.68	3.383%	$118.5596	$118.56	$118.55	$118.60
7 purchase totals =	$807.12		$863.0827	$863.09	$863.10	$863.10