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	$22.82	13.506%	$25.9021	$25.90	$25.90	$25.90
Purchase #2	$185.29	6.130%	$196.6483	$196.65	$196.65	$196.60
Purchase #3	$48.27	10.873%	$53.5184	$53.52	$53.50	$53.50
Purchase #4	$198.80	12.463%	$223.5764	$223.58	$223.60	$223.60
Purchase #5	$107.65	13.628%	$122.3205	$122.32	$122.30	$122.30
Purchase #6	$184.78	10.497%	$204.1764	$204.18	$204.20	$204.20
Purchase #7	$186.86	5.706%	$197.5222	$197.52	$197.50	$197.50
7 purchase totals =	$934.47		$1,023.6643	$1,023.67	$1,023.65	$1,023.60