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	$95.71	13.735%	$108.8558	$108.86	$108.85	$108.90
Purchase #2	$162.86	5.276%	$171.4525	$171.45	$171.45	$171.50
Purchase #3	$238.54	5.168%	$250.8677	$250.87	$250.85	$250.90
Purchase #4	$38.45	11.680%	$42.941	$42.94	$42.95	$42.90
Purchase #5	$152.81	5.375%	$161.0235	$161.02	$161.00	$161.00
Purchase #6	$231.86	3.484%	$239.938	$239.94	$239.95	$239.90
Purchase #7	$148.97	12.389%	$167.4259	$167.43	$167.45	$167.40
7 purchase totals =	$1,069.20		$1,142.5044	$1,142.51	$1,142.50	$1,142.50