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 $216.43   4.292%   $225.7192   $225.72   $225.70   $225.70  
  Purchase #2 $56.27   7.147%   $60.2916   $60.29   $60.30   $60.30  
  Purchase #3 $96.36   7.393%   $103.4839   $103.48   $103.50   $103.50  
  Purchase #4 $147.43   10.350%   $162.689   $162.69   $162.70   $162.70  
  Purchase #5 $168.92   6.865%   $180.5164   $180.52   $180.50   $180.50  
  Purchase #6 $154.89   5.684%   $163.6939   $163.69   $163.70   $163.70  
  Purchase #7 $174.33   10.198%   $192.1082   $192.11   $192.10   $192.10  
  7 purchase totals = $1,014.63       $1,088.5022   $1,088.50   $1,088.50   $1,088.50