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	$14.57	12.756%	$16.4285	$16.43	$16.45	$16.40
Purchase #2	$242.52	7.734%	$261.2765	$261.28	$261.30	$261.30
Purchase #3	$148.89	3.355%	$153.8853	$153.89	$153.90	$153.90
Purchase #4	$59.70	13.679%	$67.8664	$67.87	$67.85	$67.90
Purchase #5	$134.28	12.719%	$151.3591	$151.36	$151.35	$151.40
Purchase #6	$216.79	13.429%	$245.9027	$245.90	$245.90	$245.90
Purchase #7	$147.45	6.269%	$156.6936	$156.69	$156.70	$156.70
7 purchase totals =	$964.20		$1,053.4121	$1,053.42	$1,053.45	$1,053.50