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 $53.55   8.735%   $58.2276   $58.23   $58.25   $58.20  
  Purchase #2 $186.46   8.469%   $202.2513   $202.25   $202.25   $202.30  
  Purchase #3 $247.96   6.149%   $263.2071   $263.21   $263.20   $263.20  
  Purchase #4 $237.96   7.334%   $255.412   $255.41   $255.40   $255.40  
  Purchase #5 $116.49   8.371%   $126.2414   $126.24   $126.25   $126.20  
  Purchase #6 $13.75   4.620%   $14.3853   $14.39   $14.40   $14.40  
  Purchase #7 $154.46   12.512%   $173.786   $173.79   $173.80   $173.80  
  7 purchase totals = $1,010.63       $1,093.5107   $1,093.52   $1,093.55   $1,093.50