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 $82.26   13.586%   $93.4358   $93.44   $93.45   $93.40  
  Purchase #2 $221.72   10.660%   $245.3554   $245.36   $245.35   $245.40  
  Purchase #3 $111.63   12.439%   $125.5157   $125.52   $125.50   $125.50  
  Purchase #4 $96.27   3.238%   $99.3872   $99.39   $99.40   $99.40  
  Purchase #5 $139.83   5.700%   $147.8003   $147.80   $147.80   $147.80  
  Purchase #6 $240.81   9.804%   $264.419   $264.42   $264.40   $264.40  
  Purchase #7 $167.66   5.371%   $176.665   $176.67   $176.65   $176.70  
  7 purchase totals = $1,060.18       $1,152.5784   $1,152.60   $1,152.55   $1,152.60