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	$143.47	9.773%	$157.4913	$157.49	$157.50	$157.50
Purchase #2	$81.74	11.454%	$91.1025	$91.10	$91.10	$91.10
Purchase #3	$112.90	11.688%	$126.0958	$126.10	$126.10	$126.10
Purchase #4	$64.89	11.774%	$72.5301	$72.53	$72.55	$72.50
Purchase #5	$34.50	11.838%	$38.5841	$38.58	$38.60	$38.60
Purchase #6	$76.89	13.128%	$86.9841	$86.98	$87.00	$87.00
Purchase #7	$209.51	5.827%	$221.7181	$221.72	$221.70	$221.70
7 purchase totals =	$723.90		$794.5060	$794.50	$794.55	$794.50