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	$164.34	9.806%	$180.4552	$180.46	$180.45	$180.50
Purchase #2	$55.25	7.618%	$59.4589	$59.46	$59.45	$59.50
Purchase #3	$12.82	11.288%	$14.2671	$14.27	$14.25	$14.30
Purchase #4	$24.43	12.284%	$27.431	$27.43	$27.45	$27.40
Purchase #5	$36.98	10.140%	$40.7298	$40.73	$40.75	$40.70
Purchase #6	$112.48	6.182%	$119.4335	$119.43	$119.45	$119.40
Purchase #7	$238.60	5.605%	$251.9735	$251.97	$251.95	$252.00
7 purchase totals =	$644.90		$693.7490	$693.75	$693.75	$693.80