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 $72.77   4.411%   $75.9799   $75.98   $76.00   $76.00  
  Purchase #2 $110.92   8.483%   $120.3293   $120.33   $120.35   $120.30  
  Purchase #3 $167.96   8.128%   $181.6118   $181.61   $181.60   $181.60  
  Purchase #4 $99.39   5.473%   $104.8296   $104.83   $104.85   $104.80  
  Purchase #5 $162.26   10.443%   $179.2048   $179.20   $179.20   $179.20  
  Purchase #6 $193.65   10.516%   $214.0142   $214.01   $214.00   $214.00  
  Purchase #7 $230.92   4.794%   $241.9903   $241.99   $242.00   $242.00  
  7 purchase totals = $1,037.87       $1,117.9599   $1,117.95   $1,118.00   $1,117.90