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	$112.53	10.757%	$124.6349	$124.63	$124.65	$124.60
Purchase #2	$234.52	3.362%	$242.4046	$242.40	$242.40	$242.40
Purchase #3	$31.28	13.595%	$35.5325	$35.53	$35.55	$35.50
Purchase #4	$221.38	9.129%	$241.5898	$241.59	$241.60	$241.60
Purchase #5	$217.56	4.449%	$227.2392	$227.24	$227.25	$227.20
Purchase #6	$71.88	9.110%	$78.4283	$78.43	$78.45	$78.40
Purchase #7	$63.53	5.616%	$67.0978	$67.10	$67.10	$67.10
7 purchase totals =	$952.68		$1,016.9271	$1,016.92	$1,017.00	$1,016.80