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	$90.78	13.231%	$102.7911	$102.79	$102.80	$102.80
Purchase #2	$43.72	4.410%	$45.6481	$45.65	$45.65	$45.60
Purchase #3	$94.79	4.284%	$98.8508	$98.85	$98.85	$98.90
Purchase #4	$184.73	12.858%	$208.4826	$208.48	$208.50	$208.50
Purchase #5	$225.61	3.110%	$232.6265	$232.63	$232.65	$232.60
Purchase #6	$32.42	12.687%	$36.5331	$36.53	$36.55	$36.50
Purchase #7	$66.82	7.601%	$71.899	$71.90	$71.90	$71.90
7 purchase totals =	$738.87		$796.8312	$796.83	$796.90	$796.80