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	$122.43	7.449%	$131.5498	$131.55	$131.55	$131.50
Purchase #2	$165.72	7.758%	$178.5766	$178.58	$178.60	$178.60
Purchase #3	$86.50	10.273%	$95.3861	$95.39	$95.40	$95.40
Purchase #4	$139.52	5.311%	$146.9299	$146.93	$146.95	$146.90
Purchase #5	$86.76	5.802%	$91.7938	$91.79	$91.80	$91.80
Purchase #6	$224.81	5.644%	$237.4983	$237.50	$237.50	$237.50
Purchase #7	$158.98	6.264%	$168.9385	$168.94	$168.95	$168.90
7 purchase totals =	$984.72		$1,050.6730	$1,050.68	$1,050.75	$1,050.60