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 $98.81   3.555%   $102.3227   $102.32   $102.30   $102.30  
  Purchase #2 $187.91   8.386%   $203.6681   $203.67   $203.65   $203.70  
  Purchase #3 $238.72   6.282%   $253.7164   $253.72   $253.70   $253.70  
  Purchase #4 $223.46   6.189%   $237.2899   $237.29   $237.30   $237.30  
  Purchase #5 $75.96   5.786%   $80.355   $80.36   $80.35   $80.40  
  Purchase #6 $18.38   4.369%   $19.183   $19.18   $19.20   $19.20  
  Purchase #7 $151.78   9.637%   $166.407   $166.41   $166.40   $166.40  
  7 purchase totals = $995.02       $1,062.9421   $1,062.95   $1,062.90   $1,063.00