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	$54.66	5.848%	$57.8565	$57.86	$57.85	$57.90
Purchase #2	$221.91	3.602%	$229.9032	$229.90	$229.90	$229.90
Purchase #3	$131.41	8.630%	$142.7507	$142.75	$142.75	$142.80
Purchase #4	$241.94	9.429%	$264.7525	$264.75	$264.75	$264.80
Purchase #5	$123.96	11.706%	$138.4708	$138.47	$138.45	$138.50
Purchase #6	$147.48	11.756%	$164.8177	$164.82	$164.80	$164.80
Purchase #7	$238.56	11.417%	$265.7964	$265.80	$265.80	$265.80
7 purchase totals =	$1,159.92		$1,264.3478	$1,264.35	$1,264.30	$1,264.50