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 $178.48   9.582%   $195.582   $195.58   $195.60   $195.60  
  Purchase #2 $219.72   3.838%   $228.1529   $228.15   $228.15   $228.20  
  Purchase #3 $10.64   3.838%   $11.0484   $11.05   $11.05   $11.00  
  Purchase #4 $26.55   11.509%   $29.6056   $29.61   $29.60   $29.60  
  Purchase #5 $89.27   12.208%   $100.1681   $100.17   $100.15   $100.20  
  Purchase #6 $248.75   5.444%   $262.292   $262.29   $262.30   $262.30  
  Purchase #7 $8.48   5.279%   $8.9277   $8.93   $8.95   $8.90  
  7 purchase totals = $781.89       $835.7767   $835.78   $835.80   $835.80