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	$213.41	9.868%	$234.4693	$234.47	$234.45	$234.50
Purchase #2	$92.42	13.576%	$104.9669	$104.97	$104.95	$105.00
Purchase #3	$172.87	10.831%	$191.5935	$191.59	$191.60	$191.60
Purchase #4	$181.40	7.765%	$195.4857	$195.49	$195.50	$195.50
Purchase #5	$124.58	13.700%	$141.6475	$141.65	$141.65	$141.60
Purchase #6	$57.90	11.758%	$64.7079	$64.71	$64.70	$64.70
Purchase #7	$231.46	10.485%	$255.7286	$255.73	$255.75	$255.70
7 purchase totals =	$1,074.04		$1,188.5994	$1,188.61	$1,188.60	$1,188.60