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	$161.59	7.361%	$173.4846	$173.48	$173.50	$173.50
Purchase #2	$220.33	11.638%	$245.972	$245.97	$245.95	$246.00
Purchase #3	$26.45	11.495%	$29.4904	$29.49	$29.50	$29.50
Purchase #4	$87.79	13.252%	$99.4239	$99.42	$99.40	$99.40
Purchase #5	$156.85	3.556%	$162.4276	$162.43	$162.45	$162.40
Purchase #6	$116.58	7.652%	$125.5007	$125.50	$125.50	$125.50
Purchase #7	$227.86	7.771%	$245.567	$245.57	$245.55	$245.60
7 purchase totals =	$997.45		$1,081.8662	$1,081.86	$1,081.85	$1,081.90