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	$28.55	11.555%	$31.849	$31.85	$31.85	$31.80
Purchase #2	$63.85	13.231%	$72.298	$72.30	$72.30	$72.30
Purchase #3	$23.87	5.317%	$25.1392	$25.14	$25.15	$25.10
Purchase #4	$136.80	8.764%	$148.7892	$148.79	$148.80	$148.80
Purchase #5	$76.25	6.776%	$81.4167	$81.42	$81.40	$81.40
Purchase #6	$189.26	3.628%	$196.1264	$196.13	$196.15	$196.10
Purchase #7	$96.87	13.108%	$109.5677	$109.57	$109.55	$109.60
7 purchase totals =	$615.45		$665.1862	$665.20	$665.20	$665.10