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	$200.89	8.674%	$218.3152	$218.32	$218.30	$218.30
Purchase #2	$249.76	12.329%	$280.5529	$280.55	$280.55	$280.60
Purchase #3	$77.41	5.591%	$81.738	$81.74	$81.75	$81.70
Purchase #4	$88.25	4.834%	$92.516	$92.52	$92.50	$92.50
Purchase #5	$63.48	13.535%	$72.072	$72.07	$72.05	$72.10
Purchase #6	$95.73	7.298%	$102.7164	$102.72	$102.70	$102.70
Purchase #7	$211.55	8.321%	$229.1531	$229.15	$229.15	$229.20
7 purchase totals =	$987.07		$1,077.0636	$1,077.07	$1,077.00	$1,077.10