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	$140.82	3.271%	$145.4262	$145.43	$145.45	$145.40
Purchase #2	$126.58	11.419%	$141.0342	$141.03	$141.05	$141.00
Purchase #3	$225.52	10.626%	$249.4838	$249.48	$249.50	$249.50
Purchase #4	$124.98	7.810%	$134.7409	$134.74	$134.75	$134.70
Purchase #5	$155.35	10.401%	$171.508	$171.51	$171.50	$171.50
Purchase #6	$196.39	13.636%	$223.1697	$223.17	$223.15	$223.20
Purchase #7	$174.90	8.552%	$189.8574	$189.86	$189.85	$189.90
7 purchase totals =	$1,144.54		$1,255.2202	$1,255.22	$1,255.25	$1,255.20