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 $134.43   9.332%   $146.975   $146.98   $147.00   $147.00  
  Purchase #2 $61.53   6.129%   $65.3012   $65.30   $65.30   $65.30  
  Purchase #3 $180.45   3.140%   $186.1161   $186.12   $186.10   $186.10  
  Purchase #4 $235.68   5.848%   $249.4626   $249.46   $249.45   $249.50  
  Purchase #5 $62.69   11.202%   $69.7125   $69.71   $69.70   $69.70  
  Purchase #6 $91.88   4.185%   $95.7252   $95.73   $95.75   $95.70  
  Purchase #7 $183.92   9.309%   $201.0411   $201.04   $201.05   $201.00  
  7 purchase totals = $950.58       $1,014.3337   $1,014.34   $1,014.35   $1,014.30