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 $162.92   11.254%   $181.255   $181.26   $181.25   $181.30  
  Purchase #2 $178.61   8.649%   $194.058   $194.06   $194.05   $194.10  
  Purchase #3 $204.65   10.829%   $226.8115   $226.81   $226.80   $226.80  
  Purchase #4 $155.29   10.285%   $171.2616   $171.26   $171.25   $171.30  
  Purchase #5 $6.38   10.619%   $7.0575   $7.06   $7.05   $7.10  
  Purchase #6 $214.27   10.728%   $237.2569   $237.26   $237.25   $237.30  
  Purchase #7 $41.38   10.503%   $45.7261   $45.73   $45.75   $45.70  
  7 purchase totals = $963.50       $1,063.4266   $1,063.44   $1,063.40   $1,063.60