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   10.147%   $216.7693   $216.77   $216.75   $216.80  
  Purchase #2 $192.78   10.834%   $213.6658   $213.67   $213.65   $213.70  
  Purchase #3 $163.57   10.531%   $180.7956   $180.80   $180.80   $180.80  
  Purchase #4 $196.70   6.521%   $209.5268   $209.53   $209.55   $209.50  
  Purchase #5 $68.90   7.405%   $74.002   $74.00   $74.00   $74.00  
  Purchase #6 $233.58   7.297%   $250.6243   $250.62   $250.60   $250.60  
  Purchase #7 $242.63   10.801%   $268.8365   $268.84   $268.85   $268.80  
  7 purchase totals = $1,294.96       $1,414.2203   $1,414.23   $1,414.20   $1,414.20