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 $10.26   8.207%   $11.102   $11.10   $11.10   $11.10  
  Purchase #2 $88.63   5.614%   $93.6057   $93.61   $93.60   $93.60  
  Purchase #3 $180.72   11.753%   $201.96   $201.96   $201.95   $202.00  
  Purchase #4 $228.42   8.389%   $247.5822   $247.58   $247.60   $247.60  
  Purchase #5 $231.37   4.534%   $241.8603   $241.86   $241.85   $241.90  
  Purchase #6 $123.27   8.155%   $133.3227   $133.32   $133.30   $133.30  
  Purchase #7 $177.80   10.398%   $196.2876   $196.29   $196.30   $196.30  
  7 purchase totals = $1,040.47       $1,125.7205   $1,125.72   $1,125.70   $1,125.80