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 $62.96   9.432%   $68.8984   $68.90   $68.90   $68.90  
  Purchase #2 $60.96   13.868%   $69.4139   $69.41   $69.40   $69.40  
  Purchase #3 $247.26   6.820%   $264.1231   $264.12   $264.10   $264.10  
  Purchase #4 $185.40   10.570%   $204.9968   $205.00   $205.00   $205.00  
  Purchase #5 $43.47   9.591%   $47.6392   $47.64   $47.65   $47.60  
  Purchase #6 $63.47   8.874%   $69.1023   $69.10   $69.10   $69.10  
  Purchase #7 $194.88   9.234%   $212.8752   $212.88   $212.90   $212.90  
  7 purchase totals = $858.40       $937.0489   $937.05   $937.05   $937.00