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 $230.60   6.549%   $245.702   $245.70   $245.70   $245.70  
  Purchase #2 $71.98   4.236%   $75.0291   $75.03   $75.05   $75.00  
  Purchase #3 $63.49   3.246%   $65.5509   $65.55   $65.55   $65.60  
  Purchase #4 $142.58   12.401%   $160.2613   $160.26   $160.25   $160.30  
  Purchase #5 $197.99   6.387%   $210.6356   $210.64   $210.65   $210.60  
  Purchase #6 $135.89   7.751%   $146.4228   $146.42   $146.40   $146.40  
  Purchase #7 $205.72   4.787%   $215.5678   $215.57   $215.55   $215.60  
  7 purchase totals = $1,048.25       $1,119.1695   $1,119.17   $1,119.15   $1,119.20