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	$192.96	10.853%	$213.9019	$213.90	$213.90	$213.90
Purchase #2	$132.59	5.103%	$139.3561	$139.36	$139.35	$139.40
Purchase #3	$111.87	3.791%	$116.111	$116.11	$116.10	$116.10
Purchase #4	$117.75	12.834%	$132.862	$132.86	$132.85	$132.90
Purchase #5	$18.35	13.467%	$20.8212	$20.82	$20.80	$20.80
Purchase #6	$92.87	6.828%	$99.2112	$99.21	$99.20	$99.20
Purchase #7	$182.73	11.402%	$203.5649	$203.56	$203.55	$203.60
7 purchase totals =	$849.12		$925.8283	$925.82	$925.75	$925.90