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 $176.91   10.712%   $195.8606   $195.86   $195.85   $195.90  
  Purchase #2 $184.42   8.338%   $199.7969   $199.80   $199.80   $199.80  
  Purchase #3 $91.84   6.737%   $98.0273   $98.03   $98.05   $98.00  
  Purchase #4 $163.39   8.364%   $177.0559   $177.06   $177.05   $177.10  
  Purchase #5 $205.37   7.373%   $220.5119   $220.51   $220.50   $220.50  
  Purchase #6 $203.35   9.741%   $223.1583   $223.16   $223.15   $223.20  
  Purchase #7 $18.29   8.544%   $19.8527   $19.85   $19.85   $19.90  
  7 purchase totals = $1,043.57       $1,134.2636   $1,134.27   $1,134.25   $1,134.40