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 $41.52   13.204%   $47.0023   $47.00   $47.00   $47.00  
  Purchase #2 $246.67   5.139%   $259.3464   $259.35   $259.35   $259.30  
  Purchase #3 $84.83   7.272%   $90.9988   $91.00   $91.00   $91.00  
  Purchase #4 $170.29   9.725%   $186.8507   $186.85   $186.85   $186.90  
  Purchase #5 $119.64   6.823%   $127.803   $127.80   $127.80   $127.80  
  Purchase #6 $238.92   5.582%   $252.2565   $252.26   $252.25   $252.30  
  Purchase #7 $224.43   13.469%   $254.6585   $254.66   $254.65   $254.70  
  7 purchase totals = $1,126.30       $1,218.9162   $1,218.92   $1,218.90   $1,219.00