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 $64.47   12.191%   $72.3295   $72.33   $72.35   $72.30  
  Purchase #2 $216.31   4.861%   $226.8248   $226.82   $226.80   $226.80  
  Purchase #3 $59.41   10.790%   $65.8203   $65.82   $65.80   $65.80  
  Purchase #4 $186.89   5.681%   $197.5072   $197.51   $197.50   $197.50  
  Purchase #5 $223.62   13.775%   $254.4237   $254.42   $254.40   $254.40  
  Purchase #6 $109.91   11.460%   $122.5057   $122.51   $122.50   $122.50  
  Purchase #7 $195.74   4.651%   $204.8439   $204.84   $204.85   $204.80  
  7 purchase totals = $1,056.35       $1,144.2551   $1,144.25   $1,144.20   $1,144.10