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 $70.67   5.463%   $74.5307   $74.53   $74.55   $74.50  
  Purchase #2 $173.61   13.360%   $196.8043   $196.80   $196.80   $196.80  
  Purchase #3 $117.96   3.370%   $121.9353   $121.94   $121.95   $121.90  
  Purchase #4 $127.47   12.864%   $143.8677   $143.87   $143.85   $143.90  
  Purchase #5 $193.29   10.517%   $213.6183   $213.62   $213.60   $213.60  
  Purchase #6 $187.91   6.528%   $200.1768   $200.18   $200.20   $200.20  
  Purchase #7 $55.41   10.453%   $61.202   $61.20   $61.20   $61.20  
  7 purchase totals = $926.32       $1,012.1351   $1,012.14   $1,012.15   $1,012.10