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 $214.74   13.450%   $243.6225   $243.62   $243.60   $243.60  
  Purchase #2 $137.47   6.278%   $146.1004   $146.10   $146.10   $146.10  
  Purchase #3 $58.60   7.730%   $63.1298   $63.13   $63.15   $63.10  
  Purchase #4 $43.70   5.579%   $46.138   $46.14   $46.15   $46.10  
  Purchase #5 $238.92   5.344%   $251.6879   $251.69   $251.70   $251.70  
  Purchase #6 $174.98   3.187%   $180.5566   $180.56   $180.55   $180.60  
  Purchase #7 $240.34   10.823%   $266.352   $266.35   $266.35   $266.40  
  7 purchase totals = $1,108.75       $1,197.5872   $1,197.59   $1,197.60   $1,197.60