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 $69.32   3.502%   $71.7476   $71.75   $71.75   $71.70  
  Purchase #2 $89.49   10.323%   $98.7281   $98.73   $98.75   $98.70  
  Purchase #3 $102.29   4.521%   $106.9145   $106.91   $106.90   $106.90  
  Purchase #4 $159.99   13.237%   $181.1679   $181.17   $181.15   $181.20  
  Purchase #5 $98.36   13.529%   $111.6671   $111.67   $111.65   $111.70  
  Purchase #6 $234.73   9.548%   $257.142   $257.14   $257.15   $257.10  
  Purchase #7 $203.82   5.799%   $215.6395   $215.64   $215.65   $215.60  
  7 purchase totals = $958.00       $1,043.0067   $1,043.01   $1,043.00   $1,042.90