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	$163.91	4.310%	$170.9745	$170.97	$170.95	$171.00
Purchase #2	$217.77	8.487%	$236.2521	$236.25	$236.25	$236.30
Purchase #3	$86.50	4.172%	$90.1088	$90.11	$90.10	$90.10
Purchase #4	$26.33	5.781%	$27.8521	$27.85	$27.85	$27.90
Purchase #5	$31.52	9.751%	$34.5935	$34.59	$34.60	$34.60
Purchase #6	$39.91	6.295%	$42.4223	$42.42	$42.40	$42.40
Purchase #7	$86.94	11.210%	$96.686	$96.69	$96.70	$96.70
7 purchase totals =	$652.88		$698.8893	$698.88	$698.85	$699.00