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 $68.74   10.649%   $76.0601   $76.06   $76.05   $76.10  
  Purchase #2 $50.31   12.461%   $56.5791   $56.58   $56.60   $56.60  
  Purchase #3 $99.53   13.684%   $113.1497   $113.15   $113.15   $113.10  
  Purchase #4 $170.94   3.283%   $176.552   $176.55   $176.55   $176.60  
  Purchase #5 $194.44   8.409%   $210.7905   $210.79   $210.80   $210.80  
  Purchase #6 $212.82   4.803%   $223.0417   $223.04   $223.05   $223.00  
  Purchase #7 $181.34   8.681%   $197.0821   $197.08   $197.10   $197.10  
  7 purchase totals = $978.12       $1,053.2552   $1,053.25   $1,053.30   $1,053.30