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	$225.50	13.388%	$255.6899	$255.69	$255.70	$255.70
Purchase #2	$126.79	7.655%	$136.4958	$136.50	$136.50	$136.50
Purchase #3	$83.45	9.580%	$91.4445	$91.44	$91.45	$91.40
Purchase #4	$65.89	8.783%	$71.6771	$71.68	$71.70	$71.70
Purchase #5	$163.94	4.432%	$171.2058	$171.21	$171.20	$171.20
Purchase #6	$186.53	12.358%	$209.5814	$209.58	$209.60	$209.60
Purchase #7	$76.80	11.182%	$85.3878	$85.39	$85.40	$85.40
7 purchase totals =	$928.90		$1,021.4823	$1,021.49	$1,021.55	$1,021.50