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 $83.51   13.751%   $94.9935   $94.99   $95.00   $95.00  
  Purchase #2 $122.59   12.620%   $138.0609   $138.06   $138.05   $138.10  
  Purchase #3 $225.31   8.657%   $244.8151   $244.82   $244.80   $244.80  
  Purchase #4 $104.68   3.433%   $108.2737   $108.27   $108.25   $108.30  
  Purchase #5 $169.47   10.345%   $187.0017   $187.00   $187.00   $187.00  
  Purchase #6 $134.57   10.340%   $148.4845   $148.48   $148.50   $148.50  
  Purchase #7 $140.68   8.636%   $152.8291   $152.83   $152.85   $152.80  
  7 purchase totals = $980.81       $1,074.4585   $1,074.45   $1,074.45   $1,074.50