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 $56.37   8.224%   $61.0059   $61.01   $61.00   $61.00  
  Purchase #2 $220.37   11.862%   $246.5103   $246.51   $246.50   $246.50  
  Purchase #3 $236.82   9.573%   $259.4908   $259.49   $259.50   $259.50  
  Purchase #4 $113.98   6.850%   $121.7876   $121.79   $121.80   $121.80  
  Purchase #5 $165.55   5.491%   $174.6404   $174.64   $174.65   $174.60  
  Purchase #6 $210.74   5.536%   $222.4066   $222.41   $222.40   $222.40  
  Purchase #7 $63.95   3.533%   $66.2094   $66.21   $66.20   $66.20  
  7 purchase totals = $1,067.78       $1,152.0510   $1,152.06   $1,152.05   $1,152.00