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 $211.96   11.320%   $235.9539   $235.95   $235.95   $236.00  
  Purchase #2 $209.91   7.328%   $225.2922   $225.29   $225.30   $225.30  
  Purchase #3 $126.53   9.547%   $138.6098   $138.61   $138.60   $138.60  
  Purchase #4 $205.70   4.524%   $215.0059   $215.01   $215.00   $215.00  
  Purchase #5 $197.33   13.485%   $223.94   $223.94   $223.95   $223.90  
  Purchase #6 $171.49   6.463%   $182.5734   $182.57   $182.55   $182.60  
  Purchase #7 $92.59   9.290%   $101.1916   $101.19   $101.20   $101.20  
  7 purchase totals = $1,215.51       $1,322.5668   $1,322.56   $1,322.55   $1,322.60