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 $243.98   7.651%   $262.6469   $262.65   $262.65   $262.60  
  Purchase #2 $116.60   7.445%   $125.2809   $125.28   $125.30   $125.30  
  Purchase #3 $216.80   11.262%   $241.216   $241.22   $241.20   $241.20  
  Purchase #4 $68.84   7.558%   $74.0429   $74.04   $74.05   $74.00  
  Purchase #5 $92.65   11.190%   $103.0175   $103.02   $103.00   $103.00  
  Purchase #6 $175.50   12.225%   $196.9549   $196.95   $196.95   $197.00  
  Purchase #7 $94.90   10.262%   $104.6386   $104.64   $104.65   $104.60  
  7 purchase totals = $1,009.27       $1,107.7977   $1,107.80   $1,107.80   $1,107.70