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 $223.31   4.220%   $232.7337   $232.73   $232.75   $232.70  
  Purchase #2 $228.65   5.507%   $241.2418   $241.24   $241.25   $241.20  
  Purchase #3 $119.51   10.445%   $131.9928   $131.99   $132.00   $132.00  
  Purchase #4 $199.72   3.250%   $206.2109   $206.21   $206.20   $206.20  
  Purchase #5 $102.85   11.425%   $114.6006   $114.60   $114.60   $114.60  
  Purchase #6 $88.30   6.107%   $93.6925   $93.69   $93.70   $93.70  
  Purchase #7 $191.75   5.386%   $202.0777   $202.08   $202.10   $202.10  
  7 purchase totals = $1,154.09       $1,222.5500   $1,222.54   $1,222.60   $1,222.50