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	$137.47	11.342%	$153.0618	$153.06	$153.05	$153.10
Purchase #2	$101.58	7.154%	$108.847	$108.85	$108.85	$108.80
Purchase #3	$231.96	10.307%	$255.8681	$255.87	$255.85	$255.90
Purchase #4	$11.39	9.148%	$12.432	$12.43	$12.45	$12.40
Purchase #5	$42.69	13.507%	$48.4561	$48.46	$48.45	$48.50
Purchase #6	$185.48	5.819%	$196.2731	$196.27	$196.25	$196.30
Purchase #7	$216.78	11.650%	$242.0349	$242.03	$242.05	$242.00
7 purchase totals =	$927.35		$1,016.9730	$1,016.97	$1,016.95	$1,017.00