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	$104.64	7.613%	$112.6062	$112.61	$112.60	$112.60
Purchase #2	$60.93	9.274%	$66.5806	$66.58	$66.60	$66.60
Purchase #3	$17.90	13.773%	$20.3654	$20.37	$20.35	$20.40
Purchase #4	$139.64	9.287%	$152.6084	$152.61	$152.60	$152.60
Purchase #5	$13.48	11.295%	$15.0026	$15.00	$15.00	$15.00
Purchase #6	$160.66	4.334%	$167.623	$167.62	$167.60	$167.60
Purchase #7	$73.83	4.189%	$76.9227	$76.92	$76.90	$76.90
7 purchase totals =	$571.08		$611.7089	$611.71	$611.65	$611.70