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	$156.38	12.478%	$175.8931	$175.89	$175.90	$175.90
Purchase #2	$153.45	4.652%	$160.5885	$160.59	$160.60	$160.60
Purchase #3	$6.92	13.840%	$7.8777	$7.88	$7.90	$7.90
Purchase #4	$112.84	9.363%	$123.4052	$123.41	$123.40	$123.40
Purchase #5	$121.90	9.819%	$133.8694	$133.87	$133.85	$133.90
Purchase #6	$227.89	13.118%	$257.7846	$257.78	$257.80	$257.80
Purchase #7	$229.63	3.567%	$237.8209	$237.82	$237.80	$237.80
7 purchase totals =	$1,009.01		$1,097.2394	$1,097.24	$1,097.25	$1,097.30