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	$113.82	8.763%	$123.794	$123.79	$123.80	$123.80
Purchase #2	$120.49	9.143%	$131.5064	$131.51	$131.50	$131.50
Purchase #3	$220.87	13.664%	$251.0497	$251.05	$251.05	$251.00
Purchase #4	$216.38	13.240%	$245.0287	$245.03	$245.05	$245.00
Purchase #5	$26.59	3.822%	$27.6063	$27.61	$27.60	$27.60
Purchase #6	$78.64	8.380%	$85.23	$85.23	$85.25	$85.20
Purchase #7	$128.36	13.722%	$145.9736	$145.97	$145.95	$146.00
7 purchase totals =	$905.15		$1,010.1887	$1,010.19	$1,010.20	$1,010.10