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 $113.77   8.612%   $123.5679   $123.57   $123.55   $123.60  
  Purchase #2 $216.42   6.335%   $230.1302   $230.13   $230.15   $230.10  
  Purchase #3 $164.50   7.564%   $176.9428   $176.94   $176.95   $176.90  
  Purchase #4 $106.33   4.344%   $110.949   $110.95   $110.95   $110.90  
  Purchase #5 $138.71   6.433%   $147.6332   $147.63   $147.65   $147.60  
  Purchase #6 $12.63   12.606%   $14.2221   $14.22   $14.20   $14.20  
  Purchase #7 $232.77   10.282%   $256.7034   $256.70   $256.70   $256.70  
  7 purchase totals = $985.13       $1,060.1486   $1,060.14   $1,060.15   $1,060.00