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 $66.82   4.161%   $69.6004   $69.60   $69.60   $69.60  
  Purchase #2 $193.89   7.837%   $209.0852   $209.09   $209.10   $209.10  
  Purchase #3 $22.53   11.859%   $25.2018   $25.20   $25.20   $25.20  
  Purchase #4 $191.35   10.614%   $211.6599   $211.66   $211.65   $211.70  
  Purchase #5 $151.65   10.641%   $167.7871   $167.79   $167.80   $167.80  
  Purchase #6 $202.53   3.664%   $209.9507   $209.95   $209.95   $210.00  
  Purchase #7 $247.88   11.481%   $276.3391   $276.34   $276.35   $276.30  
  7 purchase totals = $1,076.65       $1,169.6242   $1,169.63   $1,169.65   $1,169.70