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	$166.57	3.527%	$172.4449	$172.44	$172.45	$172.40
Purchase #2	$56.39	6.206%	$59.8896	$59.89	$59.90	$59.90
Purchase #3	$104.61	4.719%	$109.5465	$109.55	$109.55	$109.50
Purchase #4	$34.81	5.631%	$36.7702	$36.77	$36.75	$36.80
Purchase #5	$59.40	12.642%	$66.9093	$66.91	$66.90	$66.90
Purchase #6	$63.31	9.785%	$69.5049	$69.50	$69.50	$69.50
Purchase #7	$114.29	3.659%	$118.4719	$118.47	$118.45	$118.50
7 purchase totals =	$599.38		$633.5373	$633.53	$633.50	$633.50