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 $173.81   13.111%   $196.5982   $196.60   $196.60   $196.60  
  Purchase #2 $204.40   4.336%   $213.2628   $213.26   $213.25   $213.30  
  Purchase #3 $35.92   10.733%   $39.7753   $39.78   $39.80   $39.80  
  Purchase #4 $43.98   10.793%   $48.7268   $48.73   $48.75   $48.70  
  Purchase #5 $220.86   11.333%   $245.8901   $245.89   $245.90   $245.90  
  Purchase #6 $225.39   9.808%   $247.4963   $247.50   $247.50   $247.50  
  Purchase #7 $190.74   6.809%   $203.7275   $203.73   $203.75   $203.70  
  7 purchase totals = $1,095.10       $1,195.4770   $1,195.49   $1,195.55   $1,195.50