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 $86.49   7.522%   $92.9958   $93.00   $93.00   $93.00  
  Purchase #2 $238.98   10.640%   $264.4075   $264.41   $264.40   $264.40  
  Purchase #3 $69.41   11.254%   $77.2214   $77.22   $77.20   $77.20  
  Purchase #4 $117.91   4.797%   $123.5661   $123.57   $123.55   $123.60  
  Purchase #5 $200.88   4.550%   $210.02   $210.02   $210.00   $210.00  
  Purchase #6 $66.38   6.341%   $70.5892   $70.59   $70.60   $70.60  
  Purchase #7 $163.25   12.264%   $183.271   $183.27   $183.25   $183.30  
  7 purchase totals = $943.30       $1,022.0710   $1,022.08   $1,022.00   $1,022.10