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 $56.63   9.850%   $62.2081   $62.21   $62.20   $62.20  
  Purchase #2 $166.65   4.812%   $174.6692   $174.67   $174.65   $174.70  
  Purchase #3 $110.41   4.455%   $115.3288   $115.33   $115.35   $115.30  
  Purchase #4 $189.59   12.754%   $213.7703   $213.77   $213.75   $213.80  
  Purchase #5 $230.43   4.562%   $240.9422   $240.94   $240.95   $240.90  
  Purchase #6 $104.93   3.851%   $108.9709   $108.97   $108.95   $109.00  
  Purchase #7 $185.77   13.353%   $210.5759   $210.58   $210.60   $210.60  
  7 purchase totals = $1,044.41       $1,126.4654   $1,126.47   $1,126.45   $1,126.50