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 $84.74   12.609%   $95.4249   $95.42   $95.40   $95.40  
  Purchase #2 $88.64   3.438%   $91.6874   $91.69   $91.70   $91.70  
  Purchase #3 $69.25   12.192%   $77.693   $77.69   $77.70   $77.70  
  Purchase #4 $166.75   4.308%   $173.9336   $173.93   $173.95   $173.90  
  Purchase #5 $100.70   9.701%   $110.4689   $110.47   $110.45   $110.50  
  Purchase #6 $196.44   4.448%   $205.1777   $205.18   $205.20   $205.20  
  Purchase #7 $244.77   4.706%   $256.2889   $256.29   $256.30   $256.30  
  7 purchase totals = $951.29       $1,010.6744   $1,010.67   $1,010.70   $1,010.70