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 $206.60   6.815%   $220.6798   $220.68   $220.70   $220.70  
  Purchase #2 $128.70   6.580%   $137.1685   $137.17   $137.15   $137.20  
  Purchase #3 $63.66   11.781%   $71.1598   $71.16   $71.15   $71.20  
  Purchase #4 $158.47   5.331%   $166.918   $166.92   $166.90   $166.90  
  Purchase #5 $22.68   6.731%   $24.2066   $24.21   $24.20   $24.20  
  Purchase #6 $231.59   5.144%   $243.503   $243.50   $243.50   $243.50  
  Purchase #7 $142.44   5.518%   $150.2998   $150.30   $150.30   $150.30  
  7 purchase totals = $954.14       $1,013.9355   $1,013.94   $1,013.90   $1,014.00