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 $62.67   13.251%   $70.9744   $70.97   $70.95   $71.00  
  Purchase #2 $189.42   7.742%   $204.0849   $204.08   $204.10   $204.10  
  Purchase #3 $81.73   8.387%   $88.5847   $88.58   $88.60   $88.60  
  Purchase #4 $224.43   7.565%   $241.4081   $241.41   $241.40   $241.40  
  Purchase #5 $199.73   11.655%   $223.0085   $223.01   $223.00   $223.00  
  Purchase #6 $149.91   5.360%   $157.9452   $157.95   $157.95   $157.90  
  Purchase #7 $8.95   3.542%   $9.267   $9.27   $9.25   $9.30  
  7 purchase totals = $916.84       $995.2728   $995.27   $995.25   $995.30