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	$189.60	13.533%	$215.2586	$215.26	$215.25	$215.30
Purchase #2	$85.97	5.725%	$90.8918	$90.89	$90.90	$90.90
Purchase #3	$35.87	12.303%	$40.2831	$40.28	$40.30	$40.30
Purchase #4	$180.81	9.803%	$198.5348	$198.53	$198.55	$198.50
Purchase #5	$218.95	5.643%	$231.3053	$231.31	$231.30	$231.30
Purchase #6	$112.57	12.784%	$126.9609	$126.96	$126.95	$127.00
Purchase #7	$96.39	11.238%	$107.2223	$107.22	$107.20	$107.20
7 purchase totals =	$920.16		$1,010.4568	$1,010.45	$1,010.45	$1,010.50