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	$41.65	11.144%	$46.2915	$46.29	$46.30	$46.30
Purchase #2	$123.91	9.802%	$136.0557	$136.06	$136.05	$136.10
Purchase #3	$63.47	12.164%	$71.1905	$71.19	$71.20	$71.20
Purchase #4	$220.60	10.421%	$243.5887	$243.59	$243.60	$243.60
Purchase #5	$107.55	11.126%	$119.516	$119.52	$119.50	$119.50
Purchase #6	$217.27	9.288%	$237.45	$237.45	$237.45	$237.50
Purchase #7	$151.28	10.610%	$167.3308	$167.33	$167.35	$167.30
7 purchase totals =	$925.73		$1,021.4232	$1,021.43	$1,021.45	$1,021.50