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 $132.84   13.701%   $151.0404   $151.04   $151.05   $151.00  
  Purchase #2 $135.39   8.449%   $146.8291   $146.83   $146.85   $146.80  
  Purchase #3 $137.85   11.361%   $153.5111   $153.51   $153.50   $153.50  
  Purchase #4 $126.98   6.236%   $134.8985   $134.90   $134.90   $134.90  
  Purchase #5 $136.32   4.517%   $142.4776   $142.48   $142.50   $142.50  
  Purchase #6 $76.86   12.241%   $86.2684   $86.27   $86.25   $86.30  
  Purchase #7 $194.73   3.259%   $201.0763   $201.08   $201.10   $201.10  
  7 purchase totals = $940.97       $1,016.1014   $1,016.11   $1,016.15   $1,016.10