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	$45.83	4.592%	$47.9345	$47.93	$47.95	$47.90
Purchase #2	$248.89	10.259%	$274.4236	$274.42	$274.40	$274.40
Purchase #3	$17.73	13.578%	$20.1374	$20.14	$20.15	$20.10
Purchase #4	$174.93	12.505%	$196.805	$196.81	$196.80	$196.80
Purchase #5	$63.45	5.413%	$66.8845	$66.88	$66.90	$66.90
Purchase #6	$234.93	11.264%	$261.3925	$261.39	$261.40	$261.40
Purchase #7	$94.45	4.646%	$98.8381	$98.84	$98.85	$98.80
7 purchase totals =	$880.21		$966.4156	$966.41	$966.45	$966.30