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 $87.49   9.304%   $95.6301   $95.63   $95.65   $95.60  
  Purchase #2 $50.95   8.861%   $55.4647   $55.46   $55.45   $55.50  
  Purchase #3 $131.28   7.644%   $141.315   $141.32   $141.30   $141.30  
  Purchase #4 $180.64   13.370%   $204.7916   $204.79   $204.80   $204.80  
  Purchase #5 $215.40   3.802%   $223.5895   $223.59   $223.60   $223.60  
  Purchase #6 $114.31   6.501%   $121.7413   $121.74   $121.75   $121.70  
  Purchase #7 $165.38   10.767%   $183.1865   $183.19   $183.20   $183.20  
  7 purchase totals = $945.45       $1,025.7187   $1,025.72   $1,025.75   $1,025.70