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	$201.52	8.108%	$217.8592	$217.86	$217.85	$217.90
Purchase #2	$158.84	4.263%	$165.6113	$165.61	$165.60	$165.60
Purchase #3	$229.84	3.511%	$237.9097	$237.91	$237.90	$237.90
Purchase #4	$147.96	7.213%	$158.6324	$158.63	$158.65	$158.60
Purchase #5	$213.43	6.584%	$227.4822	$227.48	$227.50	$227.50
Purchase #6	$75.76	8.794%	$82.4223	$82.42	$82.40	$82.40
Purchase #7	$37.71	13.154%	$42.6704	$42.67	$42.65	$42.70
7 purchase totals =	$1,065.06		$1,132.5875	$1,132.58	$1,132.55	$1,132.60