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 $216.65   7.692%   $233.3147   $233.31   $233.30   $233.30  
  Purchase #2 $149.79   5.490%   $158.0135   $158.01   $158.00   $158.00  
  Purchase #3 $59.56   9.159%   $65.0151   $65.02   $65.00   $65.00  
  Purchase #4 $217.71   8.646%   $236.5332   $236.53   $236.55   $236.50  
  Purchase #5 $229.66   4.439%   $239.8546   $239.85   $239.85   $239.90  
  Purchase #6 $88.84   9.790%   $97.5374   $97.54   $97.55   $97.50  
  Purchase #7 $86.80   4.544%   $90.7442   $90.74   $90.75   $90.70  
  7 purchase totals = $1,049.01       $1,121.0127   $1,121.00   $1,121.00   $1,120.90