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	$216.80	11.307%	$241.3136	$241.31	$241.30	$241.30
Purchase #2	$87.46	8.308%	$94.7262	$94.73	$94.75	$94.70
Purchase #3	$16.33	7.707%	$17.5886	$17.59	$17.60	$17.60
Purchase #4	$177.27	12.181%	$198.8633	$198.86	$198.85	$198.90
Purchase #5	$79.67	7.319%	$85.501	$85.50	$85.50	$85.50
Purchase #6	$57.63	10.806%	$63.8575	$63.86	$63.85	$63.90
Purchase #7	$228.72	12.113%	$256.4249	$256.42	$256.40	$256.40
7 purchase totals =	$863.88		$958.2751	$958.27	$958.25	$958.30