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	$212.41	6.292%	$225.7748	$225.77	$225.75	$225.80
Purchase #2	$81.83	11.111%	$90.9221	$90.92	$90.90	$90.90
Purchase #3	$114.50	5.807%	$121.149	$121.15	$121.15	$121.10
Purchase #4	$49.61	5.182%	$52.1808	$52.18	$52.20	$52.20
Purchase #5	$65.38	10.330%	$72.1338	$72.13	$72.15	$72.10
Purchase #6	$64.82	4.546%	$67.7667	$67.77	$67.75	$67.80
Purchase #7	$64.67	7.629%	$69.6037	$69.60	$69.60	$69.60
7 purchase totals =	$653.22		$699.5309	$699.52	$699.50	$699.50