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	$69.60	13.366%	$78.9027	$78.90	$78.90	$78.90
Purchase #2	$91.86	10.788%	$101.7699	$101.77	$101.75	$101.80
Purchase #3	$6.83	8.164%	$7.3876	$7.39	$7.40	$7.40
Purchase #4	$90.51	13.349%	$102.5922	$102.59	$102.60	$102.60
Purchase #5	$159.63	12.314%	$179.2868	$179.29	$179.30	$179.30
Purchase #6	$150.67	6.294%	$160.1532	$160.15	$160.15	$160.20
Purchase #7	$224.91	13.861%	$256.0848	$256.08	$256.10	$256.10
7 purchase totals =	$794.01		$886.1772	$886.17	$886.20	$886.30