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 $162.98   7.521%   $175.2377   $175.24   $175.25   $175.20  
  Purchase #2 $228.39   6.172%   $242.4862   $242.49   $242.50   $242.50  
  Purchase #3 $237.97   3.373%   $245.9967   $246.00   $246.00   $246.00  
  Purchase #4 $40.41   5.137%   $42.4859   $42.49   $42.50   $42.50  
  Purchase #5 $11.44   10.776%   $12.6728   $12.67   $12.65   $12.70  
  Purchase #6 $169.55   3.587%   $175.6318   $175.63   $175.65   $175.60  
  Purchase #7 $200.33   5.718%   $211.7849   $211.78   $211.80   $211.80  
  7 purchase totals = $1,051.07       $1,106.2960   $1,106.30   $1,106.35   $1,106.30