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	$147.66	8.748%	$160.5773	$160.58	$160.60	$160.60
Purchase #2	$27.68	7.439%	$29.7391	$29.74	$29.75	$29.70
Purchase #3	$71.69	6.684%	$76.4818	$76.48	$76.50	$76.50
Purchase #4	$65.81	10.744%	$72.8806	$72.88	$72.90	$72.90
Purchase #5	$132.25	10.238%	$145.7898	$145.79	$145.80	$145.80
Purchase #6	$210.75	5.517%	$222.3771	$222.38	$222.40	$222.40
Purchase #7	$133.51	7.398%	$143.3871	$143.39	$143.40	$143.40
7 purchase totals =	$789.35		$851.2328	$851.24	$851.35	$851.30