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	$135.31	8.518%	$146.8357	$146.84	$146.85	$146.80
Purchase #2	$14.52	5.733%	$15.3524	$15.35	$15.35	$15.40
Purchase #3	$6.41	12.807%	$7.2309	$7.23	$7.25	$7.20
Purchase #4	$215.68	10.475%	$238.2725	$238.27	$238.25	$238.30
Purchase #5	$115.45	13.860%	$131.4514	$131.45	$131.45	$131.50
Purchase #6	$146.84	9.351%	$160.571	$160.57	$160.55	$160.60
Purchase #7	$110.52	5.447%	$116.54	$116.54	$116.55	$116.50
7 purchase totals =	$744.73		$816.2539	$816.25	$816.25	$816.30