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 $197.98   6.384%   $210.619   $210.62   $210.60   $210.60  
  Purchase #2 $53.82   8.352%   $58.315   $58.32   $58.30   $58.30  
  Purchase #3 $239.83   12.627%   $270.1133   $270.11   $270.10   $270.10  
  Purchase #4 $41.92   10.175%   $46.1854   $46.19   $46.20   $46.20  
  Purchase #5 $164.71   12.584%   $185.4371   $185.44   $185.45   $185.40  
  Purchase #6 $171.27   6.765%   $182.8564   $182.86   $182.85   $182.90  
  Purchase #7 $95.56   11.783%   $106.8198   $106.82   $106.80   $106.80  
  7 purchase totals = $965.09       $1,060.3460   $1,060.36   $1,060.30   $1,060.30