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 $208.76   5.257%   $219.7345   $219.73   $219.75   $219.70  
  Purchase #2 $161.65   6.676%   $172.4418   $172.44   $172.45   $172.40  
  Purchase #3 $9.92   4.311%   $10.3477   $10.35   $10.35   $10.30  
  Purchase #4 $165.89   11.135%   $184.3619   $184.36   $184.35   $184.40  
  Purchase #5 $102.87   7.874%   $110.97   $110.97   $110.95   $111.00  
  Purchase #6 $244.56   7.660%   $263.2933   $263.29   $263.30   $263.30  
  Purchase #7 $50.49   4.567%   $52.7959   $52.80   $52.80   $52.80  
  7 purchase totals = $944.14       $1,013.9451   $1,013.94   $1,013.95   $1,013.90