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 $196.29   4.423%   $204.9719   $204.97   $204.95   $205.00  
  Purchase #2 $181.40   11.477%   $202.2193   $202.22   $202.20   $202.20  
  Purchase #3 $89.28   9.425%   $97.6946   $97.69   $97.70   $97.70  
  Purchase #4 $96.45   9.581%   $105.6909   $105.69   $105.70   $105.70  
  Purchase #5 $30.75   12.313%   $34.5362   $34.54   $34.55   $34.50  
  Purchase #6 $189.49   7.265%   $203.2564   $203.26   $203.25   $203.30  
  Purchase #7 $165.57   11.131%   $183.9996   $184.00   $184.00   $184.00  
  7 purchase totals = $949.23       $1,032.3689   $1,032.37   $1,032.35   $1,032.40