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	$140.27	8.779%	$152.5843	$152.58	$152.60	$152.60
Purchase #2	$141.59	13.377%	$160.5305	$160.53	$160.55	$160.50
Purchase #3	$112.64	9.712%	$123.5796	$123.58	$123.60	$123.60
Purchase #4	$204.27	7.154%	$218.8835	$218.88	$218.90	$218.90
Purchase #5	$143.84	6.157%	$152.6962	$152.70	$152.70	$152.70
Purchase #6	$69.83	9.548%	$76.4974	$76.50	$76.50	$76.50
Purchase #7	$166.57	5.517%	$175.7597	$175.76	$175.75	$175.80
7 purchase totals =	$979.01		$1,060.5312	$1,060.53	$1,060.60	$1,060.60