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 $118.49   5.519%   $125.0295   $125.03   $125.05   $125.00  
  Purchase #2 $193.66   11.459%   $215.8515   $215.85   $215.85   $215.90  
  Purchase #3 $32.58   3.350%   $33.6714   $33.67   $33.65   $33.70  
  Purchase #4 $144.26   11.843%   $161.3447   $161.34   $161.35   $161.30  
  Purchase #5 $247.85   12.515%   $278.8684   $278.87   $278.85   $278.90  
  Purchase #6 $161.45   3.618%   $167.2913   $167.29   $167.30   $167.30  
  Purchase #7 $153.27   9.316%   $167.5486   $167.55   $167.55   $167.50  
  7 purchase totals = $1,051.56       $1,149.6054   $1,149.60   $1,149.60   $1,149.60