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 $56.92   9.530%   $62.3445   $62.34   $62.35   $62.30  
  Purchase #2 $164.27   8.732%   $178.6141   $178.61   $178.60   $178.60  
  Purchase #3 $239.88   13.401%   $272.0263   $272.03   $272.05   $272.00  
  Purchase #4 $167.45   13.330%   $189.7711   $189.77   $189.75   $189.80  
  Purchase #5 $132.46   11.377%   $147.53   $147.53   $147.55   $147.50  
  Purchase #6 $138.31   3.626%   $143.3251   $143.33   $143.35   $143.30  
  Purchase #7 $112.29   11.325%   $125.0068   $125.01   $125.00   $125.00  
  7 purchase totals = $1,011.58       $1,118.6179   $1,118.62   $1,118.65   $1,118.50