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 $168.26   9.760%   $184.6822   $184.68   $184.70   $184.70  
  Purchase #2 $223.63   3.799%   $232.1257   $232.13   $232.15   $232.10  
  Purchase #3 $230.98   9.237%   $252.3156   $252.32   $252.30   $252.30  
  Purchase #4 $188.51   6.841%   $201.406   $201.41   $201.40   $201.40  
  Purchase #5 $162.33   10.823%   $179.899   $179.90   $179.90   $179.90  
  Purchase #6 $126.65   9.407%   $138.564   $138.56   $138.55   $138.60  
  Purchase #7 $233.54   12.661%   $263.1085   $263.11   $263.10   $263.10  
  7 purchase totals = $1,333.90       $1,452.1010   $1,452.11   $1,452.10   $1,452.10