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 $43.40   8.424%   $47.056   $47.06   $47.05   $47.10  
  Purchase #2 $225.50   3.659%   $233.751   $233.75   $233.75   $233.80  
  Purchase #3 $117.29   5.169%   $123.3527   $123.35   $123.35   $123.40  
  Purchase #4 $11.71   8.345%   $12.6872   $12.69   $12.70   $12.70  
  Purchase #5 $89.98   4.155%   $93.7187   $93.72   $93.70   $93.70  
  Purchase #6 $53.99   7.388%   $57.9788   $57.98   $58.00   $58.00  
  Purchase #7 $231.37   3.583%   $239.66   $239.66   $239.65   $239.70  
  7 purchase totals = $773.24       $808.2044   $808.21   $808.20   $808.40