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 $65.97   3.329%   $68.1661   $68.17   $68.15   $68.20  
  Purchase #2 $189.27   11.346%   $210.7446   $210.74   $210.75   $210.70  
  Purchase #3 $104.51   12.588%   $117.6657   $117.67   $117.65   $117.70  
  Purchase #4 $250.62   9.803%   $275.1883   $275.19   $275.20   $275.20  
  Purchase #5 $225.77   3.202%   $232.9992   $233.00   $233.00   $233.00  
  Purchase #6 $148.60   11.324%   $165.4275   $165.43   $165.45   $165.40  
  Purchase #7 $34.65   8.277%   $37.518   $37.52   $37.50   $37.50  
  7 purchase totals = $1,019.39       $1,107.7094   $1,107.72   $1,107.70   $1,107.70