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	$164.51	3.206%	$169.7842	$169.78	$169.80	$169.80
Purchase #2	$82.38	4.874%	$86.3952	$86.40	$86.40	$86.40
Purchase #3	$201.88	11.853%	$225.8088	$225.81	$225.80	$225.80
Purchase #4	$157.56	8.725%	$171.3071	$171.31	$171.30	$171.30
Purchase #5	$89.87	11.463%	$100.1718	$100.17	$100.15	$100.20
Purchase #6	$120.32	10.333%	$132.7527	$132.75	$132.75	$132.80
Purchase #7	$150.73	11.788%	$168.4981	$168.50	$168.50	$168.50
7 purchase totals =	$967.25		$1,054.7179	$1,054.72	$1,054.70	$1,054.80