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 $210.45   12.128%   $235.9734   $235.97   $235.95   $236.00  
  Purchase #2 $231.45   11.150%   $257.2567   $257.26   $257.25   $257.30  
  Purchase #3 $21.60   11.310%   $24.043   $24.04   $24.05   $24.00  
  Purchase #4 $203.79   5.778%   $215.565   $215.57   $215.55   $215.60  
  Purchase #5 $52.90   12.331%   $59.4231   $59.42   $59.40   $59.40  
  Purchase #6 $110.37   7.681%   $118.8475   $118.85   $118.85   $118.80  
  Purchase #7 $178.83   13.461%   $202.9023   $202.90   $202.90   $202.90  
  7 purchase totals = $1,009.39       $1,114.0110   $1,114.01   $1,113.95   $1,114.00