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 $211.65   12.201%   $237.4734   $237.47   $237.45   $237.50  
  Purchase #2 $216.83   13.296%   $245.6597   $245.66   $245.65   $245.70  
  Purchase #3 $23.37   10.135%   $25.7385   $25.74   $25.75   $25.70  
  Purchase #4 $54.93   6.764%   $58.6455   $58.65   $58.65   $58.60  
  Purchase #5 $181.87   11.132%   $202.1158   $202.12   $202.10   $202.10  
  Purchase #6 $200.41   7.378%   $215.1962   $215.20   $215.20   $215.20  
  Purchase #7 $75.77   5.390%   $79.854   $79.85   $79.85   $79.90  
  7 purchase totals = $964.83       $1,064.6831   $1,064.69   $1,064.65   $1,064.70