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 $90.59   5.556%   $95.6232   $95.62   $95.60   $95.60  
  Purchase #2 $181.41   12.258%   $203.6472   $203.65   $203.65   $203.60  
  Purchase #3 $231.36   8.799%   $251.7174   $251.72   $251.70   $251.70  
  Purchase #4 $25.65   11.741%   $28.6616   $28.66   $28.65   $28.70  
  Purchase #5 $50.97   6.316%   $54.1893   $54.19   $54.20   $54.20  
  Purchase #6 $148.84   8.472%   $161.4497   $161.45   $161.45   $161.40  
  Purchase #7 $226.31   10.756%   $250.6519   $250.65   $250.65   $250.70  
  7 purchase totals = $955.13       $1,045.9403   $1,045.94   $1,045.90   $1,045.90