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 $67.49   7.650%   $72.653   $72.65   $72.65   $72.70  
  Purchase #2 $248.84   8.323%   $269.551   $269.55   $269.55   $269.60  
  Purchase #3 $235.88   6.248%   $250.6178   $250.62   $250.60   $250.60  
  Purchase #4 $231.97   4.731%   $242.9445   $242.94   $242.95   $242.90  
  Purchase #5 $120.37   5.769%   $127.3141   $127.31   $127.30   $127.30  
  Purchase #6 $11.46   4.547%   $11.9811   $11.98   $12.00   $12.00  
  Purchase #7 $9.64   3.738%   $10.0003   $10.00   $10.00   $10.00  
  7 purchase totals = $925.65       $985.0618   $985.05   $985.05   $985.10