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 $179.89   7.872%   $194.0509   $194.05   $194.05   $194.10  
  Purchase #2 $22.98   10.231%   $25.3311   $25.33   $25.35   $25.30  
  Purchase #3 $151.43   7.390%   $162.6207   $162.62   $162.60   $162.60  
  Purchase #4 $158.39   11.349%   $176.3657   $176.37   $176.35   $176.40  
  Purchase #5 $208.70   9.833%   $229.2215   $229.22   $229.20   $229.20  
  Purchase #6 $195.91   10.612%   $216.7   $216.70   $216.70   $216.70  
  Purchase #7 $140.72   8.148%   $152.1859   $152.19   $152.20   $152.20  
  7 purchase totals = $1,058.02       $1,156.4758   $1,156.48   $1,156.45   $1,156.50