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 $176.53   12.217%   $198.0967   $198.10   $198.10   $198.10  
  Purchase #2 $194.91   3.135%   $201.0204   $201.02   $201.00   $201.00  
  Purchase #3 $51.57   3.513%   $53.3817   $53.38   $53.40   $53.40  
  Purchase #4 $93.87   9.250%   $102.553   $102.55   $102.55   $102.60  
  Purchase #5 $216.79   4.664%   $226.9011   $226.90   $226.90   $226.90  
  Purchase #6 $200.51   3.411%   $207.3494   $207.35   $207.35   $207.30  
  Purchase #7 $80.25   6.471%   $85.443   $85.44   $85.45   $85.40  
  7 purchase totals = $1,014.43       $1,074.7453   $1,074.74   $1,074.75   $1,074.70