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 $86.65   8.831%   $94.3021   $94.30   $94.30   $94.30  
  Purchase #2 $212.52   5.533%   $224.2787   $224.28   $224.30   $224.30  
  Purchase #3 $20.82   9.850%   $22.8708   $22.87   $22.85   $22.90  
  Purchase #4 $141.83   4.752%   $148.5698   $148.57   $148.55   $148.60  
  Purchase #5 $245.37   9.851%   $269.5414   $269.54   $269.55   $269.50  
  Purchase #6 $221.70   4.715%   $232.1532   $232.15   $232.15   $232.20  
  Purchase #7 $194.70   3.446%   $201.4094   $201.41   $201.40   $201.40  
  7 purchase totals = $1,123.59       $1,193.1254   $1,193.12   $1,193.10   $1,193.20