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	$202.83	10.644%	$224.4192	$224.42	$224.40	$224.40
Purchase #2	$72.53	8.714%	$78.8503	$78.85	$78.85	$78.90
Purchase #3	$127.85	6.489%	$136.1462	$136.15	$136.15	$136.10
Purchase #4	$191.25	9.164%	$208.7762	$208.78	$208.80	$208.80
Purchase #5	$44.53	11.482%	$49.6429	$49.64	$49.65	$49.60
Purchase #6	$28.75	12.238%	$32.2684	$32.27	$32.25	$32.30
Purchase #7	$67.53	10.214%	$74.4275	$74.43	$74.45	$74.40
7 purchase totals =	$735.27		$804.5307	$804.54	$804.55	$804.50