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 $87.69   11.582%   $97.8463   $97.85   $97.85   $97.80  
  Purchase #2 $216.80   12.393%   $243.668   $243.67   $243.65   $243.70  
  Purchase #3 $53.31   5.856%   $56.4318   $56.43   $56.45   $56.40  
  Purchase #4 $79.51   7.817%   $85.7253   $85.73   $85.75   $85.70  
  Purchase #5 $163.45   6.632%   $174.29   $174.29   $174.30   $174.30  
  Purchase #6 $102.52   11.193%   $113.9951   $114.00   $114.00   $114.00  
  Purchase #7 $30.96   7.561%   $33.3009   $33.30   $33.30   $33.30  
  7 purchase totals = $734.24       $805.2574   $805.27   $805.30   $805.20