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 $117.84   7.212%   $126.3386   $126.34   $126.35   $126.30  
  Purchase #2 $41.83   4.183%   $43.5797   $43.58   $43.60   $43.60  
  Purchase #3 $243.98   4.575%   $255.1421   $255.14   $255.15   $255.10  
  Purchase #4 $241.28   5.573%   $254.7265   $254.73   $254.75   $254.70  
  Purchase #5 $111.71   12.264%   $125.4101   $125.41   $125.40   $125.40  
  Purchase #6 $141.75   9.747%   $155.5664   $155.57   $155.55   $155.60  
  Purchase #7 $212.90   6.314%   $226.3425   $226.34   $226.35   $226.30  
  7 purchase totals = $1,111.29       $1,187.1059   $1,187.11   $1,187.15   $1,187.00