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 $54.69   13.507%   $62.077   $62.08   $62.10   $62.10  
  Purchase #2 $152.54   4.323%   $159.1343   $159.13   $159.15   $159.10  
  Purchase #3 $122.93   12.820%   $138.6896   $138.69   $138.70   $138.70  
  Purchase #4 $240.51   8.194%   $260.2174   $260.22   $260.20   $260.20  
  Purchase #5 $84.84   4.510%   $88.6663   $88.67   $88.65   $88.70  
  Purchase #6 $112.69   7.209%   $120.8138   $120.81   $120.80   $120.80  
  Purchase #7 $181.39   10.191%   $199.8755   $199.88   $199.90   $199.90  
  7 purchase totals = $949.59       $1,029.4739   $1,029.48   $1,029.50   $1,029.50