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 $136.65   11.295%   $152.0846   $152.08   $152.10   $152.10  
  Purchase #2 $180.37   8.387%   $195.4976   $195.50   $195.50   $195.50  
  Purchase #3 $141.36   10.634%   $156.3922   $156.39   $156.40   $156.40  
  Purchase #4 $192.70   7.722%   $207.5803   $207.58   $207.60   $207.60  
  Purchase #5 $212.96   12.316%   $239.1882   $239.19   $239.20   $239.20  
  Purchase #6 $22.61   9.874%   $24.8425   $24.84   $24.85   $24.80  
  Purchase #7 $42.95   10.650%   $47.5242   $47.52   $47.50   $47.50  
  7 purchase totals = $929.60       $1,023.1096   $1,023.10   $1,023.15   $1,023.10