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 $207.65   5.746%   $219.5816   $219.58   $219.60   $219.60  
  Purchase #2 $157.73   6.157%   $167.4414   $167.44   $167.45   $167.40  
  Purchase #3 $51.95   9.538%   $56.905   $56.91   $56.90   $56.90  
  Purchase #4 $203.55   12.869%   $229.7448   $229.74   $229.75   $229.70  
  Purchase #5 $197.57   3.664%   $204.809   $204.81   $204.80   $204.80  
  Purchase #6 $158.60   11.709%   $177.1705   $177.17   $177.15   $177.20  
  Purchase #7 $49.38   3.633%   $51.174   $51.17   $51.15   $51.20  
  7 purchase totals = $1,026.43       $1,106.8263   $1,106.82   $1,106.80   $1,106.80