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	$170.88	9.795%	$187.6177	$187.62	$187.60	$187.60
Purchase #2	$14.42	7.384%	$15.4848	$15.48	$15.50	$15.50
Purchase #3	$117.96	11.504%	$131.5301	$131.53	$131.55	$131.50
Purchase #4	$222.94	13.546%	$253.1395	$253.14	$253.15	$253.10
Purchase #5	$40.44	12.688%	$45.571	$45.57	$45.55	$45.60
Purchase #6	$44.26	11.355%	$49.2857	$49.29	$49.30	$49.30
Purchase #7	$182.69	7.425%	$196.2547	$196.25	$196.25	$196.30
7 purchase totals =	$793.59		$878.8835	$878.88	$878.90	$878.90