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	$140.91	5.362%	$148.4656	$148.47	$148.45	$148.50
Purchase #2	$168.87	3.337%	$174.5052	$174.51	$174.50	$174.50
Purchase #3	$248.54	12.798%	$280.3481	$280.35	$280.35	$280.30
Purchase #4	$182.30	6.749%	$194.6034	$194.60	$194.60	$194.60
Purchase #5	$147.83	9.239%	$161.488	$161.49	$161.50	$161.50
Purchase #6	$18.34	11.642%	$20.4751	$20.48	$20.50	$20.50
Purchase #7	$34.62	6.775%	$36.9655	$36.97	$36.95	$37.00
7 purchase totals =	$941.41		$1,016.8509	$1,016.87	$1,016.85	$1,016.90