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 $196.48   9.258%   $214.6701   $214.67   $214.65   $214.70  
  Purchase #2 $36.81   11.559%   $41.0649   $41.06   $41.05   $41.10  
  Purchase #3 $138.86   7.637%   $149.4647   $149.46   $149.45   $149.50  
  Purchase #4 $241.83   4.853%   $253.566   $253.57   $253.55   $253.60  
  Purchase #5 $128.35   13.857%   $146.1355   $146.14   $146.15   $146.10  
  Purchase #6 $173.34   4.224%   $180.6619   $180.66   $180.65   $180.70  
  Purchase #7 $101.68   4.752%   $106.5118   $106.51   $106.50   $106.50  
  7 purchase totals = $1,017.35       $1,092.0749   $1,092.07   $1,092.00   $1,092.20