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 $63.27   10.562%   $69.9526   $69.95   $69.95   $70.00  
  Purchase #2 $226.78   11.598%   $253.0819   $253.08   $253.10   $253.10  
  Purchase #3 $113.49   6.210%   $120.5377   $120.54   $120.55   $120.50  
  Purchase #4 $194.83   9.262%   $212.8752   $212.88   $212.90   $212.90  
  Purchase #5 $103.55   8.224%   $112.066   $112.07   $112.05   $112.10  
  Purchase #6 $140.62   9.843%   $154.4612   $154.46   $154.45   $154.50  
  Purchase #7 $75.92   12.572%   $85.4647   $85.46   $85.45   $85.50  
  7 purchase totals = $918.46       $1,008.4393   $1,008.44   $1,008.45   $1,008.60