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	$151.60	13.397%	$171.9099	$171.91	$171.90	$171.90
Purchase #2	$125.69	9.358%	$137.4521	$137.45	$137.45	$137.50
Purchase #3	$213.74	9.547%	$234.1458	$234.15	$234.15	$234.10
Purchase #4	$194.54	11.757%	$217.4121	$217.41	$217.40	$217.40
Purchase #5	$194.81	9.315%	$212.9566	$212.96	$212.95	$213.00
Purchase #6	$179.49	9.714%	$196.9257	$196.93	$196.95	$196.90
Purchase #7	$99.95	11.523%	$111.4672	$111.47	$111.45	$111.50
7 purchase totals =	$1,159.82		$1,282.2694	$1,282.28	$1,282.25	$1,282.30