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	$202.81	7.874%	$218.7793	$218.78	$218.80	$218.80
Purchase #2	$196.28	7.273%	$210.5554	$210.56	$210.55	$210.60
Purchase #3	$57.49	10.303%	$63.4132	$63.41	$63.40	$63.40
Purchase #4	$33.27	9.737%	$36.5095	$36.51	$36.50	$36.50
Purchase #5	$192.76	7.189%	$206.6175	$206.62	$206.60	$206.60
Purchase #6	$124.89	11.731%	$139.5408	$139.54	$139.55	$139.50
Purchase #7	$198.50	13.442%	$225.1824	$225.18	$225.20	$225.20
7 purchase totals =	$1,006.00		$1,100.5981	$1,100.60	$1,100.60	$1,100.60