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 $214.55   10.260%   $236.5628   $236.56   $236.55   $236.60  
  Purchase #2 $198.53   9.443%   $217.2772   $217.28   $217.30   $217.30  
  Purchase #3 $214.65   11.157%   $238.5985   $238.60   $238.60   $238.60  
  Purchase #4 $108.74   11.404%   $121.1407   $121.14   $121.15   $121.10  
  Purchase #5 $247.76   7.276%   $265.787   $265.79   $265.80   $265.80  
  Purchase #6 $218.80   11.437%   $243.8242   $243.82   $243.80   $243.80  
  Purchase #7 $199.85   7.397%   $214.6329   $214.63   $214.65   $214.60  
  7 purchase totals = $1,402.88       $1,537.8233   $1,537.82   $1,537.85   $1,537.80