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 $91.70   6.759%   $97.898   $97.90   $97.90   $97.90  
  Purchase #2 $224.48   5.682%   $237.235   $237.24   $237.25   $237.20  
  Purchase #3 $181.61   5.725%   $192.0072   $192.01   $192.00   $192.00  
  Purchase #4 $95.90   7.292%   $102.893   $102.89   $102.90   $102.90  
  Purchase #5 $95.41   6.112%   $101.2415   $101.24   $101.25   $101.20  
  Purchase #6 $184.44   11.267%   $205.2209   $205.22   $205.20   $205.20  
  Purchase #7 $217.37   3.874%   $225.7909   $225.79   $225.80   $225.80  
  7 purchase totals = $1,090.91       $1,162.2865   $1,162.29   $1,162.30   $1,162.20