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 $67.88   11.871%   $75.938   $75.94   $75.95   $75.90  
  Purchase #2 $196.92   3.853%   $204.5073   $204.51   $204.50   $204.50  
  Purchase #3 $216.52   13.253%   $245.2154   $245.22   $245.20   $245.20  
  Purchase #4 $237.93   3.657%   $246.6311   $246.63   $246.65   $246.60  
  Purchase #5 $79.38   9.743%   $87.114   $87.11   $87.10   $87.10  
  Purchase #6 $198.36   3.170%   $204.648   $204.65   $204.65   $204.60  
  Purchase #7 $107.94   8.693%   $117.3232   $117.32   $117.30   $117.30  
  7 purchase totals = $1,104.93       $1,181.3770   $1,181.38   $1,181.35   $1,181.20