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 $204.76   13.327%   $232.0484   $232.05   $232.05   $232.00  
  Purchase #2 $120.25   8.387%   $130.3354   $130.34   $130.35   $130.30  
  Purchase #3 $144.94   10.612%   $160.321   $160.32   $160.30   $160.30  
  Purchase #4 $245.67   12.666%   $276.7866   $276.79   $276.80   $276.80  
  Purchase #5 $198.97   6.656%   $212.2134   $212.21   $212.20   $212.20  
  Purchase #6 $84.69   3.815%   $87.9209   $87.92   $87.90   $87.90  
  Purchase #7 $63.87   12.666%   $71.9598   $71.96   $71.95   $72.00  
  7 purchase totals = $1,063.15       $1,171.5855   $1,171.59   $1,171.55   $1,171.50