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	$196.51	6.579%	$209.4384	$209.44	$209.45	$209.40
Purchase #2	$37.44	11.874%	$41.8856	$41.89	$41.90	$41.90
Purchase #3	$100.81	13.109%	$114.0252	$114.03	$114.05	$114.00
Purchase #4	$129.33	4.237%	$134.8097	$134.81	$134.80	$134.80
Purchase #5	$248.48	5.207%	$261.4184	$261.42	$261.40	$261.40
Purchase #6	$19.31	12.166%	$21.6593	$21.66	$21.65	$21.70
Purchase #7	$244.70	4.821%	$256.497	$256.50	$256.50	$256.50
7 purchase totals =	$976.58		$1,039.7336	$1,039.75	$1,039.75	$1,039.70