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 $191.26   7.609%   $205.813   $205.81   $205.80   $205.80  
  Purchase #2 $214.66   13.505%   $243.6498   $243.65   $243.65   $243.60  
  Purchase #3 $61.75   9.784%   $67.7916   $67.79   $67.80   $67.80  
  Purchase #4 $80.67   6.291%   $85.7449   $85.74   $85.75   $85.70  
  Purchase #5 $165.29   12.132%   $185.343   $185.34   $185.35   $185.30  
  Purchase #6 $232.58   12.856%   $262.4805   $262.48   $262.50   $262.50  
  Purchase #7 $64.56   10.563%   $71.3795   $71.38   $71.40   $71.40  
  7 purchase totals = $1,010.77       $1,122.2023   $1,122.19   $1,122.25   $1,122.10