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 $206.93   11.454%   $230.6318   $230.63   $230.65   $230.60  
  Purchase #2 $212.59   13.661%   $241.6319   $241.63   $241.65   $241.60  
  Purchase #3 $8.45   13.821%   $9.6179   $9.62   $9.60   $9.60  
  Purchase #4 $47.76   10.718%   $52.8789   $52.88   $52.90   $52.90  
  Purchase #5 $150.59   6.136%   $159.8302   $159.83   $159.85   $159.80  
  Purchase #6 $190.78   11.544%   $212.8036   $212.80   $212.80   $212.80  
  Purchase #7 $219.85   12.248%   $246.7772   $246.78   $246.80   $246.80  
  7 purchase totals = $1,036.95       $1,154.1715   $1,154.17   $1,154.25   $1,154.10