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 $216.46   8.363%   $234.5625   $234.56   $234.55   $234.60  
  Purchase #2 $191.33   9.399%   $209.3131   $209.31   $209.30   $209.30  
  Purchase #3 $24.91   10.514%   $27.529   $27.53   $27.55   $27.50  
  Purchase #4 $245.71   11.279%   $273.4236   $273.42   $273.40   $273.40  
  Purchase #5 $149.51   8.344%   $161.9851   $161.99   $162.00   $162.00  
  Purchase #6 $60.59   7.348%   $65.0422   $65.04   $65.05   $65.00  
  Purchase #7 $115.77   5.693%   $122.3608   $122.36   $122.35   $122.40  
  7 purchase totals = $1,004.28       $1,094.2163   $1,094.21   $1,094.20   $1,094.20