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	$206.32	6.440%	$219.607	$219.61	$219.60	$219.60
Purchase #2	$187.81	10.405%	$207.3516	$207.35	$207.35	$207.40
Purchase #3	$100.27	4.305%	$104.5866	$104.59	$104.60	$104.60
Purchase #4	$173.27	4.191%	$180.5317	$180.53	$180.55	$180.50
Purchase #5	$55.76	11.243%	$62.0291	$62.03	$62.05	$62.00
Purchase #6	$179.53	3.698%	$186.169	$186.17	$186.15	$186.20
Purchase #7	$132.53	9.331%	$144.8964	$144.90	$144.90	$144.90
7 purchase totals =	$1,035.49		$1,105.1714	$1,105.18	$1,105.20	$1,105.20