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 $87.76   5.695%   $92.7579   $92.76   $92.75   $92.80  
  Purchase #2 $220.97   7.270%   $237.0345   $237.03   $237.05   $237.00  
  Purchase #3 $95.31   5.722%   $100.7636   $100.76   $100.75   $100.80  
  Purchase #4 $116.60   4.161%   $121.4517   $121.45   $121.45   $121.50  
  Purchase #5 $247.94   6.814%   $264.8346   $264.83   $264.85   $264.80  
  Purchase #6 $193.68   4.743%   $202.8662   $202.87   $202.85   $202.90  
  Purchase #7 $99.29   5.720%   $104.9694   $104.97   $104.95   $105.00  
  7 purchase totals = $1,061.55       $1,124.6779   $1,124.67   $1,124.65   $1,124.80