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 $213.61   10.299%   $235.6097   $235.61   $235.60   $235.60  
  Purchase #2 $53.57   13.341%   $60.7168   $60.72   $60.70   $60.70  
  Purchase #3 $206.99   12.707%   $233.2922   $233.29   $233.30   $233.30  
  Purchase #4 $112.48   5.315%   $118.4583   $118.46   $118.45   $118.50  
  Purchase #5 $203.62   13.597%   $231.3062   $231.31   $231.30   $231.30  
  Purchase #6 $202.65   9.134%   $221.1601   $221.16   $221.15   $221.20  
  Purchase #7 $70.63   5.711%   $74.6637   $74.66   $74.65   $74.70  
  7 purchase totals = $1,063.55       $1,175.2070   $1,175.21   $1,175.15   $1,175.30