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	$17.67	3.695%	$18.3229	$18.32	$18.30	$18.30
Purchase #2	$139.93	8.641%	$152.0214	$152.02	$152.00	$152.00
Purchase #3	$72.55	5.479%	$76.525	$76.53	$76.55	$76.50
Purchase #4	$140.88	13.872%	$160.4229	$160.42	$160.40	$160.40
Purchase #5	$80.98	11.849%	$90.5753	$90.58	$90.60	$90.60
Purchase #6	$14.42	10.248%	$15.8978	$15.90	$15.90	$15.90
Purchase #7	$208.80	5.356%	$219.9833	$219.98	$220.00	$220.00
7 purchase totals =	$675.23		$733.7486	$733.75	$733.75	$733.70