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 $114.36   10.620%   $126.505   $126.51   $126.50   $126.50  
  Purchase #2 $53.58   5.734%   $56.6523   $56.65   $56.65   $56.70  
  Purchase #3 $247.79   9.718%   $271.8702   $271.87   $271.85   $271.90  
  Purchase #4 $229.72   12.319%   $258.0192   $258.02   $258.00   $258.00  
  Purchase #5 $61.78   12.744%   $69.6532   $69.65   $69.65   $69.70  
  Purchase #6 $184.42   5.641%   $194.8231   $194.82   $194.80   $194.80  
  Purchase #7 $154.40   10.602%   $170.7695   $170.77   $170.75   $170.80  
  7 purchase totals = $1,046.05       $1,148.2925   $1,148.29   $1,148.20   $1,148.40