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	$85.31	11.618%	$95.2213	$95.22	$95.20	$95.20
Purchase #2	$243.37	6.495%	$259.1769	$259.18	$259.20	$259.20
Purchase #3	$132.83	9.477%	$145.4183	$145.42	$145.40	$145.40
Purchase #4	$161.72	4.249%	$168.5915	$168.59	$168.60	$168.60
Purchase #5	$200.86	6.454%	$213.8235	$213.82	$213.80	$213.80
Purchase #6	$101.98	4.470%	$106.5385	$106.54	$106.55	$106.50
Purchase #7	$234.43	3.615%	$242.9046	$242.90	$242.90	$242.90
7 purchase totals =	$1,160.50		$1,231.6746	$1,231.67	$1,231.65	$1,231.60