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 $180.86   7.837%   $195.034   $195.03   $195.05   $195.00  
  Purchase #2 $112.79   10.741%   $124.9048   $124.90   $124.90   $124.90  
  Purchase #3 $180.74   12.452%   $203.2457   $203.25   $203.25   $203.20  
  Purchase #4 $157.92   10.680%   $174.7859   $174.79   $174.80   $174.80  
  Purchase #5 $85.87   8.449%   $93.1252   $93.13   $93.15   $93.10  
  Purchase #6 $210.89   4.236%   $219.8233   $219.82   $219.80   $219.80  
  Purchase #7 $59.97   9.863%   $65.8848   $65.88   $65.90   $65.90  
  7 purchase totals = $989.04       $1,076.8037   $1,076.80   $1,076.85   $1,076.70