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	$80.98	4.265%	$84.4338	$84.43	$84.45	$84.40
Purchase #2	$30.66	7.137%	$32.8482	$32.85	$32.85	$32.80
Purchase #3	$11.43	13.186%	$12.9372	$12.94	$12.95	$12.90
Purchase #4	$75.80	9.262%	$82.8206	$82.82	$82.80	$82.80
Purchase #5	$148.35	5.674%	$156.7674	$156.77	$156.75	$156.80
Purchase #6	$150.51	10.795%	$166.7576	$166.76	$166.75	$166.80
Purchase #7	$54.62	5.241%	$57.4826	$57.48	$57.50	$57.50
7 purchase totals =	$552.35		$594.0474	$594.05	$594.05	$594.00