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	$60.53	8.131%	$65.4517	$65.45	$65.45	$65.50
Purchase #2	$216.58	13.632%	$246.1042	$246.10	$246.10	$246.10
Purchase #3	$119.82	8.573%	$130.0922	$130.09	$130.10	$130.10
Purchase #4	$161.29	4.208%	$168.0771	$168.08	$168.10	$168.10
Purchase #5	$152.72	12.494%	$171.8008	$171.80	$171.80	$171.80
Purchase #6	$96.94	12.404%	$108.9644	$108.96	$108.95	$109.00
Purchase #7	$135.62	10.662%	$150.0798	$150.08	$150.10	$150.10
7 purchase totals =	$943.50		$1,040.5702	$1,040.56	$1,040.60	$1,040.70