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	$180.78	11.575%	$201.7053	$201.71	$201.70	$201.70
Purchase #2	$58.82	12.113%	$65.9449	$65.94	$65.95	$65.90
Purchase #3	$171.90	11.578%	$191.8026	$191.80	$191.80	$191.80
Purchase #4	$177.43	10.595%	$196.2287	$196.23	$196.25	$196.20
Purchase #5	$45.91	12.784%	$51.7791	$51.78	$51.80	$51.80
Purchase #6	$187.42	11.450%	$208.8796	$208.88	$208.90	$208.90
Purchase #7	$160.85	13.579%	$182.6918	$182.69	$182.70	$182.70
7 purchase totals =	$983.11		$1,099.0320	$1,099.03	$1,099.10	$1,099.00