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 $62.69   8.668%   $68.124   $68.12   $68.10   $68.10  
  Purchase #2 $204.26   8.620%   $221.8672   $221.87   $221.85   $221.90  
  Purchase #3 $96.33   6.382%   $102.4778   $102.48   $102.50   $102.50  
  Purchase #4 $70.72   5.729%   $74.7715   $74.77   $74.75   $74.80  
  Purchase #5 $198.93   9.158%   $217.148   $217.15   $217.15   $217.10  
  Purchase #6 $60.58   10.587%   $66.9936   $66.99   $67.00   $67.00  
  Purchase #7 $14.74   7.136%   $15.7918   $15.79   $15.80   $15.80  
  7 purchase totals = $708.25       $767.1739   $767.17   $767.15   $767.20