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 $100.39   13.583%   $114.026   $114.03   $114.05   $114.00  
  Purchase #2 $194.52   7.372%   $208.86   $208.86   $208.85   $208.90  
  Purchase #3 $205.64   12.790%   $231.9414   $231.94   $231.95   $231.90  
  Purchase #4 $245.56   12.619%   $276.5472   $276.55   $276.55   $276.50  
  Purchase #5 $37.92   3.641%   $39.3007   $39.30   $39.30   $39.30  
  Purchase #6 $79.56   9.355%   $87.0028   $87.00   $87.00   $87.00  
  Purchase #7 $225.48   8.464%   $244.5646   $244.56   $244.55   $244.60  
  7 purchase totals = $1,089.07       $1,202.2427   $1,202.24   $1,202.25   $1,202.20