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	$104.51	6.725%	$111.5383	$111.54	$111.55	$111.50
Purchase #2	$36.53	4.519%	$38.1808	$38.18	$38.20	$38.20
Purchase #3	$13.45	10.759%	$14.8971	$14.90	$14.90	$14.90
Purchase #4	$205.98	13.218%	$233.2064	$233.21	$233.20	$233.20
Purchase #5	$144.67	13.746%	$164.5563	$164.56	$164.55	$164.60
Purchase #6	$6.44	6.204%	$6.8395	$6.84	$6.85	$6.80
Purchase #7	$128.72	7.465%	$138.3289	$138.33	$138.35	$138.30
7 purchase totals =	$640.30		$707.5473	$707.56	$707.60	$707.50