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 $44.79   6.487%   $47.6955   $47.70   $47.70   $47.70  
  Purchase #2 $184.30   6.319%   $195.9459   $195.95   $195.95   $195.90  
  Purchase #3 $54.81   12.516%   $61.67   $61.67   $61.65   $61.70  
  Purchase #4 $211.57   11.584%   $236.0783   $236.08   $236.10   $236.10  
  Purchase #5 $234.71   13.305%   $265.9382   $265.94   $265.95   $265.90  
  Purchase #6 $230.33   9.498%   $252.2067   $252.21   $252.20   $252.20  
  Purchase #7 $63.83   3.310%   $65.9428   $65.94   $65.95   $65.90  
  7 purchase totals = $1,024.34       $1,125.4774   $1,125.49   $1,125.50   $1,125.40