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 $68.42   8.846%   $74.4724   $74.47   $74.45   $74.50  
  Purchase #2 $174.43   7.334%   $187.2227   $187.22   $187.20   $187.20  
  Purchase #3 $149.33   8.352%   $161.802   $161.80   $161.80   $161.80  
  Purchase #4 $182.93   8.234%   $197.9925   $197.99   $198.00   $198.00  
  Purchase #5 $224.71   9.769%   $246.6619   $246.66   $246.65   $246.70  
  Purchase #6 $235.38   11.409%   $262.2345   $262.23   $262.25   $262.20  
  Purchase #7 $85.33   13.583%   $96.9204   $96.92   $96.90   $96.90  
  7 purchase totals = $1,120.53       $1,227.3064   $1,227.29   $1,227.25   $1,227.30