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	$193.90	12.568%	$218.2694	$218.27	$218.25	$218.30
Purchase #2	$148.96	5.302%	$156.8579	$156.86	$156.85	$156.90
Purchase #3	$54.46	9.402%	$59.5803	$59.58	$59.60	$59.60
Purchase #4	$234.37	4.657%	$245.2846	$245.28	$245.30	$245.30
Purchase #5	$168.66	8.274%	$182.6149	$182.61	$182.60	$182.60
Purchase #6	$155.62	6.481%	$165.7057	$165.71	$165.70	$165.70
Purchase #7	$8.30	3.246%	$8.5694	$8.57	$8.55	$8.60
7 purchase totals =	$964.27		$1,036.8822	$1,036.88	$1,036.85	$1,037.00