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	$54.41	8.781%	$59.1877	$59.19	$59.20	$59.20
Purchase #2	$67.79	13.472%	$76.9227	$76.92	$76.90	$76.90
Purchase #3	$189.81	12.172%	$212.9137	$212.91	$212.90	$212.90
Purchase #4	$38.49	5.659%	$40.6681	$40.67	$40.65	$40.70
Purchase #5	$200.40	7.497%	$215.424	$215.42	$215.40	$215.40
Purchase #6	$170.77	4.592%	$178.6118	$178.61	$178.60	$178.60
Purchase #7	$221.45	10.472%	$244.6402	$244.64	$244.65	$244.60
7 purchase totals =	$943.12		$1,028.3682	$1,028.36	$1,028.30	$1,028.30