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	$208.51	6.540%	$222.1466	$222.15	$222.15	$222.10
Purchase #2	$68.79	6.597%	$73.3281	$73.33	$73.35	$73.30
Purchase #3	$38.27	3.443%	$39.5876	$39.59	$39.60	$39.60
Purchase #4	$125.79	5.408%	$132.5927	$132.59	$132.60	$132.60
Purchase #5	$230.91	4.735%	$241.8436	$241.84	$241.85	$241.80
Purchase #6	$225.56	10.590%	$249.4468	$249.45	$249.45	$249.40
Purchase #7	$87.27	11.821%	$97.5862	$97.59	$97.60	$97.60
7 purchase totals =	$985.10		$1,056.5316	$1,056.54	$1,056.60	$1,056.40