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	$78.25	10.413%	$86.3982	$86.40	$86.40	$86.40
Purchase #2	$37.87	7.473%	$40.7	$40.70	$40.70	$40.70
Purchase #3	$77.63	11.227%	$86.3455	$86.35	$86.35	$86.30
Purchase #4	$25.46	7.789%	$27.4431	$27.44	$27.45	$27.40
Purchase #5	$9.92	9.174%	$10.8301	$10.83	$10.85	$10.80
Purchase #6	$62.39	11.675%	$69.674	$69.67	$69.65	$69.70
Purchase #7	$62.34	6.598%	$66.4532	$66.45	$66.45	$66.50
7 purchase totals =	$353.86		$387.8441	$387.84	$387.85	$387.80