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	$93.28	7.577%	$100.3478	$100.35	$100.35	$100.30
Purchase #2	$29.40	7.226%	$31.5244	$31.52	$31.50	$31.50
Purchase #3	$25.97	12.310%	$29.1669	$29.17	$29.15	$29.20
Purchase #4	$68.38	5.115%	$71.8776	$71.88	$71.90	$71.90
Purchase #5	$241.77	8.250%	$261.716	$261.72	$261.70	$261.70
Purchase #6	$161.86	4.179%	$168.6241	$168.62	$168.60	$168.60
Purchase #7	$128.46	6.558%	$136.8844	$136.88	$136.90	$136.90
7 purchase totals =	$749.12		$800.1412	$800.14	$800.10	$800.10