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	$60.69	8.603%	$65.9112	$65.91	$65.90	$65.90
Purchase #2	$24.58	6.767%	$26.2433	$26.24	$26.25	$26.20
Purchase #3	$113.39	5.729%	$119.8861	$119.89	$119.90	$119.90
Purchase #4	$117.76	12.864%	$132.9086	$132.91	$132.90	$132.90
Purchase #5	$100.58	12.502%	$113.1545	$113.15	$113.15	$113.20
Purchase #6	$40.42	7.501%	$43.4519	$43.45	$43.45	$43.50
Purchase #7	$98.49	11.297%	$109.6164	$109.62	$109.60	$109.60
7 purchase totals =	$555.91		$611.1720	$611.17	$611.15	$611.20