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 $184.83   9.228%   $201.8861   $201.89   $201.90   $201.90  
  Purchase #2 $52.35   4.218%   $54.5581   $54.56   $54.55   $54.60  
  Purchase #3 $117.79   5.718%   $124.5252   $124.53   $124.55   $124.50  
  Purchase #4 $107.88   3.781%   $111.9589   $111.96   $111.95   $112.00  
  Purchase #5 $74.94   8.442%   $81.2664   $81.27   $81.25   $81.30  
  Purchase #6 $212.51   6.272%   $225.8386   $225.84   $225.85   $225.80  
  Purchase #7 $205.39   3.118%   $211.7941   $211.79   $211.80   $211.80  
  7 purchase totals = $955.69       $1,011.8274   $1,011.84   $1,011.85   $1,011.90