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	$64.73	4.466%	$67.6208	$67.62	$67.60	$67.60
Purchase #2	$7.64	7.716%	$8.2295	$8.23	$8.25	$8.20
Purchase #3	$7.67	3.731%	$7.9562	$7.96	$7.95	$8.00
Purchase #4	$155.90	5.527%	$164.5166	$164.52	$164.50	$164.50
Purchase #5	$234.40	9.179%	$255.9156	$255.92	$255.90	$255.90
Purchase #6	$80.37	3.455%	$83.1468	$83.15	$83.15	$83.10
Purchase #7	$200.85	4.784%	$210.4587	$210.46	$210.45	$210.50
7 purchase totals =	$751.56		$797.8442	$797.86	$797.80	$797.80