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	$118.57	5.325%	$124.8839	$124.88	$124.90	$124.90
Purchase #2	$160.54	11.843%	$179.5528	$179.55	$179.55	$179.60
Purchase #3	$56.46	12.493%	$63.5135	$63.51	$63.50	$63.50
Purchase #4	$125.27	9.473%	$137.1368	$137.14	$137.15	$137.10
Purchase #5	$182.61	7.239%	$195.8291	$195.83	$195.85	$195.80
Purchase #6	$208.60	3.312%	$215.5088	$215.51	$215.50	$215.50
Purchase #7	$208.86	10.787%	$231.3897	$231.39	$231.40	$231.40
7 purchase totals =	$1,060.91		$1,147.8146	$1,147.81	$1,147.85	$1,147.80