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 $116.85   7.784%   $125.9456   $125.95   $125.95   $125.90  
  Purchase #2 $60.35   8.776%   $65.6463   $65.65   $65.65   $65.60  
  Purchase #3 $18.35   11.366%   $20.4357   $20.44   $20.45   $20.40  
  Purchase #4 $159.94   10.674%   $177.012   $177.01   $177.00   $177.00  
  Purchase #5 $153.92   12.132%   $172.5936   $172.59   $172.60   $172.60  
  Purchase #6 $189.29   6.208%   $201.0411   $201.04   $201.05   $201.00  
  Purchase #7 $180.48   9.144%   $196.9831   $196.98   $197.00   $197.00  
  7 purchase totals = $879.18       $959.6574   $959.66   $959.70   $959.50