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 $233.83   5.196%   $245.9798   $245.98   $246.00   $246.00  
  Purchase #2 $172.53   7.814%   $186.0115   $186.01   $186.00   $186.00  
  Purchase #3 $146.68   6.259%   $155.8607   $155.86   $155.85   $155.90  
  Purchase #4 $45.92   3.564%   $47.5566   $47.56   $47.55   $47.60  
  Purchase #5 $216.58   8.398%   $234.7684   $234.77   $234.75   $234.80  
  Purchase #6 $100.53   5.254%   $105.8118   $105.81   $105.80   $105.80  
  Purchase #7 $166.36   7.299%   $178.5026   $178.50   $178.50   $178.50  
  7 purchase totals = $1,082.43       $1,154.4914   $1,154.49   $1,154.45   $1,154.60