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 $195.85   7.589%   $210.7131   $210.71   $210.70   $210.70  
  Purchase #2 $57.76   9.326%   $63.1467   $63.15   $63.15   $63.10  
  Purchase #3 $39.41   13.785%   $44.8427   $44.84   $44.85   $44.80  
  Purchase #4 $157.30   9.806%   $172.7248   $172.72   $172.70   $172.70  
  Purchase #5 $80.31   6.125%   $85.229   $85.23   $85.25   $85.20  
  Purchase #6 $204.47   12.583%   $230.1985   $230.20   $230.20   $230.20  
  Purchase #7 $242.37   4.734%   $253.8438   $253.84   $253.85   $253.80  
  7 purchase totals = $977.47       $1,060.6986   $1,060.69   $1,060.70   $1,060.50