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 $213.80   10.386%   $236.0053   $236.01   $236.00   $236.00  
  Purchase #2 $96.77   10.317%   $106.7538   $106.75   $106.75   $106.80  
  Purchase #3 $87.83   10.436%   $96.9959   $97.00   $97.00   $97.00  
  Purchase #4 $34.95   7.362%   $37.523   $37.52   $37.50   $37.50  
  Purchase #5 $62.96   10.435%   $69.5299   $69.53   $69.55   $69.50  
  Purchase #6 $132.99   13.456%   $150.8851   $150.89   $150.90   $150.90  
  Purchase #7 $181.71   11.544%   $202.6866   $202.69   $202.70   $202.70  
  7 purchase totals = $811.01       $900.3796   $900.39   $900.40   $900.40