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 $97.25   8.711%   $105.7214   $105.72   $105.70   $105.70  
  Purchase #2 $213.58   4.251%   $222.6593   $222.66   $222.65   $222.70  
  Purchase #3 $160.53   4.515%   $167.7779   $167.78   $167.80   $167.80  
  Purchase #4 $203.93   10.751%   $225.8545   $225.85   $225.85   $225.90  
  Purchase #5 $249.48   4.239%   $260.0555   $260.06   $260.05   $260.10  
  Purchase #6 $232.89   3.676%   $241.451   $241.45   $241.45   $241.50  
  Purchase #7 $56.33   13.485%   $63.9261   $63.93   $63.95   $63.90  
  7 purchase totals = $1,213.99       $1,287.4457   $1,287.45   $1,287.45   $1,287.60