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 $43.69   3.392%   $45.172   $45.17   $45.15   $45.20  
  Purchase #2 $159.86   4.447%   $166.969   $166.97   $166.95   $167.00  
  Purchase #3 $182.55   11.519%   $203.5779   $203.58   $203.60   $203.60  
  Purchase #4 $189.87   6.533%   $202.2742   $202.27   $202.25   $202.30  
  Purchase #5 $110.55   4.860%   $115.9227   $115.92   $115.90   $115.90  
  Purchase #6 $179.46   3.835%   $186.3423   $186.34   $186.35   $186.30  
  Purchase #7 $24.26   5.587%   $25.6154   $25.62   $25.60   $25.60  
  7 purchase totals = $890.24       $945.8735   $945.87   $945.80   $945.90