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	$192.61	9.336%	$210.5921	$210.59	$210.60	$210.60
Purchase #2	$5.29	3.535%	$5.477	$5.48	$5.50	$5.50
Purchase #3	$64.83	11.536%	$72.3088	$72.31	$72.30	$72.30
Purchase #4	$139.99	5.382%	$147.5243	$147.52	$147.50	$147.50
Purchase #5	$86.97	4.472%	$90.8593	$90.86	$90.85	$90.90
Purchase #6	$110.97	11.713%	$123.9679	$123.97	$123.95	$124.00
Purchase #7	$12.78	7.838%	$13.7817	$13.78	$13.80	$13.80
7 purchase totals =	$613.44		$664.5111	$664.51	$664.50	$664.60