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	$34.49	7.200%	$36.9733	$36.97	$36.95	$37.00
Purchase #2	$224.83	13.272%	$254.6694	$254.67	$254.65	$254.70
Purchase #3	$57.59	4.660%	$60.2737	$60.27	$60.25	$60.30
Purchase #4	$69.38	13.705%	$78.8885	$78.89	$78.90	$78.90
Purchase #5	$108.86	3.409%	$112.571	$112.57	$112.55	$112.60
Purchase #6	$203.31	9.548%	$222.722	$222.72	$222.70	$222.70
Purchase #7	$227.62	3.478%	$235.5366	$235.54	$235.55	$235.50
7 purchase totals =	$926.08		$1,001.6345	$1,001.63	$1,001.55	$1,001.70