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	$186.35	11.573%	$207.9163	$207.92	$207.90	$207.90
Purchase #2	$81.48	3.523%	$84.3505	$84.35	$84.35	$84.40
Purchase #3	$247.27	13.417%	$280.4462	$280.45	$280.45	$280.40
Purchase #4	$248.77	12.665%	$280.2767	$280.28	$280.30	$280.30
Purchase #5	$211.48	12.683%	$238.302	$238.30	$238.30	$238.30
Purchase #6	$200.52	6.517%	$213.5879	$213.59	$213.60	$213.60
Purchase #7	$190.62	5.214%	$200.5589	$200.56	$200.55	$200.60
7 purchase totals =	$1,366.49		$1,505.4385	$1,505.45	$1,505.45	$1,505.50