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	$146.58	6.455%	$156.0417	$156.04	$156.05	$156.00
Purchase #2	$181.37	6.177%	$192.5732	$192.57	$192.55	$192.60
Purchase #3	$124.94	12.498%	$140.555	$140.56	$140.55	$140.60
Purchase #4	$102.80	13.710%	$116.8939	$116.89	$116.90	$116.90
Purchase #5	$156.63	10.392%	$172.907	$172.91	$172.90	$172.90
Purchase #6	$90.73	13.625%	$103.092	$103.09	$103.10	$103.10
Purchase #7	$213.89	12.618%	$240.8786	$240.88	$240.90	$240.90
7 purchase totals =	$1,016.94		$1,122.9414	$1,122.94	$1,122.95	$1,123.00