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 $196.44   4.523%   $205.325   $205.33   $205.35   $205.30  
  Purchase #2 $236.52   13.483%   $268.41   $268.41   $268.40   $268.40  
  Purchase #3 $36.26   8.666%   $39.4023   $39.40   $39.40   $39.40  
  Purchase #4 $113.88   12.765%   $128.4168   $128.42   $128.40   $128.40  
  Purchase #5 $82.84   10.241%   $91.3236   $91.32   $91.30   $91.30  
  Purchase #6 $153.57   6.414%   $163.42   $163.42   $163.40   $163.40  
  Purchase #7 $43.85   12.532%   $49.3453   $49.35   $49.35   $49.30  
  7 purchase totals = $863.36       $945.6430   $945.65   $945.60   $945.50