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 $213.55   8.755%   $232.2463   $232.25   $232.25   $232.20  
  Purchase #2 $67.47   5.607%   $71.253   $71.25   $71.25   $71.30  
  Purchase #3 $212.50   7.344%   $228.106   $228.11   $228.10   $228.10  
  Purchase #4 $122.40   9.253%   $133.7257   $133.73   $133.75   $133.70  
  Purchase #5 $186.87   11.185%   $207.7714   $207.77   $207.75   $207.80  
  Purchase #6 $60.48   5.751%   $63.9582   $63.96   $63.95   $64.00  
  Purchase #7 $202.70   10.454%   $223.8903   $223.89   $223.90   $223.90  
  7 purchase totals = $1,065.97       $1,160.9509   $1,160.96   $1,160.95   $1,161.00