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 $186.63   5.563%   $197.0122   $197.01   $197.00   $197.00  
  Purchase #2 $141.96   3.197%   $146.4985   $146.50   $146.50   $146.50  
  Purchase #3 $176.47   13.774%   $200.777   $200.78   $200.80   $200.80  
  Purchase #4 $74.93   7.666%   $80.6741   $80.67   $80.65   $80.70  
  Purchase #5 $137.48   9.564%   $150.6286   $150.63   $150.65   $150.60  
  Purchase #6 $206.46   12.365%   $231.9888   $231.99   $232.00   $232.00  
  Purchase #7 $59.28   4.220%   $61.7816   $61.78   $61.80   $61.80  
  7 purchase totals = $983.21       $1,069.3608   $1,069.36   $1,069.40   $1,069.40