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 $88.74   5.365%   $93.5009   $93.50   $93.50   $93.50  
  Purchase #2 $200.53   7.555%   $215.68   $215.68   $215.70   $215.70  
  Purchase #3 $42.34   7.773%   $45.6311   $45.63   $45.65   $45.60  
  Purchase #4 $219.57   11.371%   $244.5373   $244.54   $244.55   $244.50  
  Purchase #5 $205.68   5.136%   $216.2437   $216.24   $216.25   $216.20  
  Purchase #6 $198.76   8.449%   $215.5532   $215.55   $215.55   $215.60  
  Purchase #7 $184.67   6.707%   $197.0558   $197.06   $197.05   $197.10  
  7 purchase totals = $1,140.29       $1,228.2020   $1,228.20   $1,228.25   $1,228.20