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	$219.48	7.433%	$235.7939	$235.79	$235.80	$235.80
Purchase #2	$169.46	9.759%	$185.9976	$186.00	$186.00	$186.00
Purchase #3	$61.56	7.797%	$66.3598	$66.36	$66.35	$66.40
Purchase #4	$179.59	6.260%	$190.8323	$190.83	$190.85	$190.80
Purchase #5	$241.97	13.483%	$274.5948	$274.59	$274.60	$274.60
Purchase #6	$55.65	8.744%	$60.516	$60.52	$60.50	$60.50
Purchase #7	$37.40	12.631%	$42.124	$42.12	$42.10	$42.10
7 purchase totals =	$965.11		$1,056.2184	$1,056.21	$1,056.20	$1,056.20