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	$118.38	4.333%	$123.5094	$123.51	$123.50	$123.50
Purchase #2	$200.99	8.734%	$218.5445	$218.54	$218.55	$218.50
Purchase #3	$55.81	6.690%	$59.5437	$59.54	$59.55	$59.50
Purchase #4	$25.97	7.730%	$27.9775	$27.98	$28.00	$28.00
Purchase #5	$74.61	10.121%	$82.1613	$82.16	$82.15	$82.20
Purchase #6	$114.91	9.554%	$125.8885	$125.89	$125.90	$125.90
Purchase #7	$63.77	3.828%	$66.2111	$66.21	$66.20	$66.20
7 purchase totals =	$654.44		$703.8360	$703.83	$703.85	$703.80