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 $113.38   11.368%   $126.269   $126.27   $126.25   $126.30  
  Purchase #2 $186.90   8.133%   $202.1006   $202.10   $202.10   $202.10  
  Purchase #3 $99.70   6.565%   $106.2453   $106.25   $106.25   $106.20  
  Purchase #4 $167.41   4.603%   $175.1159   $175.12   $175.10   $175.10  
  Purchase #5 $123.55   4.838%   $129.5273   $129.53   $129.55   $129.50  
  Purchase #6 $73.56   8.517%   $79.8251   $79.83   $79.85   $79.80  
  Purchase #7 $241.73   3.183%   $249.4243   $249.42   $249.40   $249.40  
  7 purchase totals = $1,006.23       $1,068.5075   $1,068.52   $1,068.50   $1,068.40