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 $112.34   11.586%   $125.3557   $125.36   $125.35   $125.40  
  Purchase #2 $202.53   13.265%   $229.3956   $229.40   $229.40   $229.40  
  Purchase #3 $96.75   13.646%   $109.9525   $109.95   $109.95   $110.00  
  Purchase #4 $218.58   9.191%   $238.6697   $238.67   $238.65   $238.70  
  Purchase #5 $240.38   4.562%   $251.3461   $251.35   $251.35   $251.30  
  Purchase #6 $151.55   11.245%   $168.5918   $168.59   $168.60   $168.60  
  Purchase #7 $80.79   5.710%   $85.4031   $85.40   $85.40   $85.40  
  7 purchase totals = $1,102.92       $1,208.7145   $1,208.72   $1,208.70   $1,208.80