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 $219.79   8.156%   $237.7161   $237.72   $237.70   $237.70  
  Purchase #2 $208.97   11.273%   $232.5272   $232.53   $232.55   $232.50  
  Purchase #3 $47.78   12.618%   $53.8089   $53.81   $53.80   $53.80  
  Purchase #4 $239.98   9.665%   $263.1741   $263.17   $263.15   $263.20  
  Purchase #5 $104.89   3.636%   $108.7038   $108.70   $108.70   $108.70  
  Purchase #6 $50.37   7.866%   $54.3321   $54.33   $54.35   $54.30  
  Purchase #7 $54.54   10.562%   $60.3005   $60.30   $60.30   $60.30  
  7 purchase totals = $926.32       $1,010.5627   $1,010.56   $1,010.55   $1,010.50