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 $61.94   12.505%   $69.6856   $69.69   $69.70   $69.70  
  Purchase #2 $204.63   8.588%   $222.2036   $222.20   $222.20   $222.20  
  Purchase #3 $245.36   4.437%   $256.2466   $256.25   $256.25   $256.20  
  Purchase #4 $94.29   13.280%   $106.8117   $106.81   $106.80   $106.80  
  Purchase #5 $246.30   3.157%   $254.0757   $254.08   $254.10   $254.10  
  Purchase #6 $37.66   9.867%   $41.3759   $41.38   $41.40   $41.40  
  Purchase #7 $203.46   6.826%   $217.3482   $217.35   $217.35   $217.30  
  7 purchase totals = $1,093.64       $1,167.7473   $1,167.76   $1,167.80   $1,167.70