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 $92.86   5.162%   $97.6534   $97.65   $97.65   $97.70  
  Purchase #2 $80.78   8.759%   $87.8555   $87.86   $87.85   $87.90  
  Purchase #3 $189.94   5.724%   $200.8122   $200.81   $200.80   $200.80  
  Purchase #4 $94.93   4.461%   $99.1648   $99.16   $99.15   $99.20  
  Purchase #5 $231.65   13.584%   $263.1173   $263.12   $263.10   $263.10  
  Purchase #6 $5.97   9.451%   $6.5342   $6.53   $6.55   $6.50  
  Purchase #7 $244.54   7.148%   $262.0197   $262.02   $262.00   $262.00  
  7 purchase totals = $940.67       $1,017.1571   $1,017.15   $1,017.10   $1,017.20