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 $94.93   7.364%   $101.9206   $101.92   $101.90   $101.90  
  Purchase #2 $189.73   5.176%   $199.5504   $199.55   $199.55   $199.60  
  Purchase #3 $79.40   6.701%   $84.7206   $84.72   $84.70   $84.70  
  Purchase #4 $94.98   5.765%   $100.4556   $100.46   $100.45   $100.50  
  Purchase #5 $129.91   3.646%   $134.6465   $134.65   $134.65   $134.60  
  Purchase #6 $113.88   5.504%   $120.148   $120.15   $120.15   $120.10  
  Purchase #7 $250.66   13.795%   $285.2385   $285.24   $285.25   $285.20  
  7 purchase totals = $953.49       $1,026.6802   $1,026.69   $1,026.65   $1,026.60