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	$212.67	13.184%	$240.7084	$240.71	$240.70	$240.70
Purchase #2	$242.59	4.236%	$252.8661	$252.87	$252.85	$252.90
Purchase #3	$52.90	13.244%	$59.9061	$59.91	$59.90	$59.90
Purchase #4	$225.41	12.217%	$252.9483	$252.95	$252.95	$252.90
Purchase #5	$30.33	10.699%	$33.575	$33.58	$33.60	$33.60
Purchase #6	$63.60	5.502%	$67.0993	$67.10	$67.10	$67.10
Purchase #7	$203.91	10.251%	$224.8128	$224.81	$224.80	$224.80
7 purchase totals =	$1,031.41		$1,131.9160	$1,131.93	$1,131.90	$1,131.90