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	$86.40	5.262%	$90.9464	$90.95	$90.95	$90.90
Purchase #2	$92.56	8.552%	$100.4757	$100.48	$100.50	$100.50
Purchase #3	$248.71	12.687%	$280.2638	$280.26	$280.25	$280.30
Purchase #4	$48.50	8.242%	$52.4974	$52.50	$52.50	$52.50
Purchase #5	$10.79	10.622%	$11.9361	$11.94	$11.95	$11.90
Purchase #6	$80.70	10.747%	$89.3728	$89.37	$89.35	$89.40
Purchase #7	$125.41	12.521%	$141.1126	$141.11	$141.10	$141.10
7 purchase totals =	$693.07		$766.6048	$766.61	$766.60	$766.60