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	$56.43	9.655%	$61.8783	$61.88	$61.90	$61.90
Purchase #2	$70.83	7.555%	$76.1812	$76.18	$76.20	$76.20
Purchase #3	$49.73	13.479%	$56.4331	$56.43	$56.45	$56.40
Purchase #4	$161.53	10.673%	$178.7701	$178.77	$178.75	$178.80
Purchase #5	$83.73	8.516%	$90.8604	$90.86	$90.85	$90.90
Purchase #6	$217.34	10.534%	$240.2346	$240.23	$240.25	$240.20
Purchase #7	$207.83	9.750%	$228.0934	$228.09	$228.10	$228.10
7 purchase totals =	$847.42		$932.4511	$932.44	$932.50	$932.50