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	$237.31	12.482%	$266.931	$266.93	$266.95	$266.90
Purchase #2	$91.59	11.398%	$102.0294	$102.03	$102.05	$102.00
Purchase #3	$133.75	7.548%	$143.8455	$143.85	$143.85	$143.80
Purchase #4	$19.27	4.537%	$20.1443	$20.14	$20.15	$20.10
Purchase #5	$16.48	12.635%	$18.5622	$18.56	$18.55	$18.60
Purchase #6	$179.39	9.427%	$196.3011	$196.30	$196.30	$196.30
Purchase #7	$192.70	12.377%	$216.5505	$216.55	$216.55	$216.60
7 purchase totals =	$870.49		$964.3640	$964.36	$964.40	$964.30