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 $183.82   7.406%   $197.4337   $197.43   $197.45   $197.40  
  Purchase #2 $200.31   4.794%   $209.9129   $209.91   $209.90   $209.90  
  Purchase #3 $77.69   6.163%   $82.478   $82.48   $82.50   $82.50  
  Purchase #4 $234.47   12.585%   $263.978   $263.98   $264.00   $264.00  
  Purchase #5 $182.89   9.866%   $200.9339   $200.93   $200.95   $200.90  
  Purchase #6 $121.49   12.741%   $136.969   $136.97   $136.95   $137.00  
  Purchase #7 $32.27   5.292%   $33.9777   $33.98   $34.00   $34.00  
  7 purchase totals = $1,032.94       $1,125.6832   $1,125.68   $1,125.75   $1,125.70