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 $95.61   9.553%   $104.7436   $104.74   $104.75   $104.70  
  Purchase #2 $228.72   6.373%   $243.2963   $243.30   $243.30   $243.30  
  Purchase #3 $129.36   3.169%   $133.4594   $133.46   $133.45   $133.50  
  Purchase #4 $173.92   5.468%   $183.4299   $183.43   $183.45   $183.40  
  Purchase #5 $154.59   6.811%   $165.1191   $165.12   $165.10   $165.10  
  Purchase #6 $228.31   8.159%   $246.9378   $246.94   $246.95   $246.90  
  Purchase #7 $39.59   5.552%   $41.788   $41.79   $41.80   $41.80  
  7 purchase totals = $1,050.10       $1,118.7741   $1,118.78   $1,118.80   $1,118.70