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	$44.35	13.489%	$50.3324	$50.33	$50.35	$50.30
Purchase #2	$11.27	6.730%	$12.0285	$12.03	$12.05	$12.00
Purchase #3	$136.77	11.653%	$152.7078	$152.71	$152.70	$152.70
Purchase #4	$235.87	8.382%	$255.6406	$255.64	$255.65	$255.60
Purchase #5	$36.56	9.840%	$40.1575	$40.16	$40.15	$40.20
Purchase #6	$248.53	5.529%	$262.2712	$262.27	$262.25	$262.30
Purchase #7	$228.76	8.785%	$248.8566	$248.86	$248.85	$248.90
7 purchase totals =	$942.11		$1,021.9946	$1,022.00	$1,022.00	$1,022.00