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 $94.99   12.620%   $106.9777   $106.98   $107.00   $107.00  
  Purchase #2 $145.44   13.438%   $164.9842   $164.98   $165.00   $165.00  
  Purchase #3 $121.54   3.259%   $125.501   $125.50   $125.50   $125.50  
  Purchase #4 $175.92   3.353%   $181.8186   $181.82   $181.80   $181.80  
  Purchase #5 $234.70   10.131%   $258.4775   $258.48   $258.50   $258.50  
  Purchase #6 $61.86   3.142%   $63.8036   $63.80   $63.80   $63.80  
  Purchase #7 $146.46   10.863%   $162.3699   $162.37   $162.35   $162.40  
  7 purchase totals = $980.91       $1,063.9325   $1,063.93   $1,063.95   $1,064.00