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 $197.65   10.781%   $218.9586   $218.96   $218.95   $219.00  
  Purchase #2 $205.50   13.734%   $233.7234   $233.72   $233.70   $233.70  
  Purchase #3 $98.33   12.190%   $110.3164   $110.32   $110.30   $110.30  
  Purchase #4 $7.92   6.692%   $8.45   $8.45   $8.45   $8.50  
  Purchase #5 $145.25   11.672%   $162.2036   $162.20   $162.20   $162.20  
  Purchase #6 $203.46   6.128%   $215.928   $215.93   $215.95   $215.90  
  Purchase #7 $93.39   8.171%   $101.0209   $101.02   $101.00   $101.00  
  7 purchase totals = $951.50       $1,050.6009   $1,050.60   $1,050.55   $1,050.60