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 $196.80   3.123%   $202.9461   $202.95   $202.95   $202.90  
  Purchase #2 $23.92   8.585%   $25.9735   $25.97   $25.95   $26.00  
  Purchase #3 $106.51   13.717%   $121.12   $121.12   $121.10   $121.10  
  Purchase #4 $112.75   13.168%   $127.5969   $127.60   $127.60   $127.60  
  Purchase #5 $150.45   4.336%   $156.9735   $156.97   $156.95   $157.00  
  Purchase #6 $239.32   9.632%   $262.3713   $262.37   $262.35   $262.40  
  Purchase #7 $200.60   10.556%   $221.7753   $221.78   $221.80   $221.80  
  7 purchase totals = $1,030.35       $1,118.7566   $1,118.76   $1,118.70   $1,118.80