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	$59.76	12.616%	$67.2993	$67.30	$67.30	$67.30
Purchase #2	$121.91	8.649%	$132.454	$132.45	$132.45	$132.50
Purchase #3	$137.71	13.604%	$156.4441	$156.44	$156.45	$156.40
Purchase #4	$185.62	13.339%	$210.3799	$210.38	$210.40	$210.40
Purchase #5	$97.89	3.775%	$101.5853	$101.59	$101.60	$101.60
Purchase #6	$108.32	3.347%	$111.9455	$111.95	$111.95	$111.90
Purchase #7	$104.65	7.625%	$112.6296	$112.63	$112.65	$112.60
7 purchase totals =	$815.86		$892.7377	$892.74	$892.80	$892.70