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 $195.52   4.147%   $203.6282   $203.63   $203.65   $203.60  
  Purchase #2 $45.43   3.654%   $47.09   $47.09   $47.10   $47.10  
  Purchase #3 $172.64   9.677%   $189.3464   $189.35   $189.35   $189.30  
  Purchase #4 $215.87   7.568%   $232.207   $232.21   $232.20   $232.20  
  Purchase #5 $198.88   10.162%   $219.0902   $219.09   $219.10   $219.10  
  Purchase #6 $169.41   4.716%   $177.3994   $177.40   $177.40   $177.40  
  Purchase #7 $44.29   10.390%   $48.8917   $48.89   $48.90   $48.90  
  7 purchase totals = $1,042.04       $1,117.6529   $1,117.66   $1,117.70   $1,117.60