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 $24.43   6.262%   $25.9598   $25.96   $25.95   $26.00  
  Purchase #2 $182.65   8.263%   $197.7424   $197.74   $197.75   $197.70  
  Purchase #3 $220.88   6.700%   $235.679   $235.68   $235.70   $235.70  
  Purchase #4 $74.59   11.843%   $83.4237   $83.42   $83.40   $83.40  
  Purchase #5 $85.79   9.685%   $94.0988   $94.10   $94.10   $94.10  
  Purchase #6 $44.85   4.656%   $46.9382   $46.94   $46.95   $46.90  
  Purchase #7 $187.67   12.370%   $210.8848   $210.88   $210.90   $210.90  
  7 purchase totals = $820.86       $894.7267   $894.72   $894.75   $894.70