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	$96.33	3.246%	$99.4569	$99.46	$99.45	$99.50
Purchase #2	$66.73	11.223%	$74.2191	$74.22	$74.20	$74.20
Purchase #3	$119.65	8.779%	$130.1541	$130.15	$130.15	$130.20
Purchase #4	$196.80	10.688%	$217.834	$217.83	$217.85	$217.80
Purchase #5	$136.81	11.551%	$152.6129	$152.61	$152.60	$152.60
Purchase #6	$234.71	10.405%	$259.1316	$259.13	$259.15	$259.10
Purchase #7	$10.73	9.660%	$11.7665	$11.77	$11.75	$11.80
7 purchase totals =	$861.76		$945.1751	$945.17	$945.15	$945.20