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 $58.59   6.340%   $62.3046   $62.30   $62.30   $62.30  
  Purchase #2 $246.43   12.789%   $277.9459   $277.95   $277.95   $277.90  
  Purchase #3 $94.44   13.256%   $106.959   $106.96   $106.95   $107.00  
  Purchase #4 $203.71   6.230%   $216.4011   $216.40   $216.40   $216.40  
  Purchase #5 $108.85   12.770%   $122.7501   $122.75   $122.75   $122.80  
  Purchase #6 $207.96   12.547%   $234.0527   $234.05   $234.05   $234.10  
  Purchase #7 $208.82   5.263%   $219.8102   $219.81   $219.80   $219.80  
  7 purchase totals = $1,128.80       $1,240.2236   $1,240.22   $1,240.20   $1,240.30