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 $193.48   11.603%   $215.9295   $215.93   $215.95   $215.90  
  Purchase #2 $64.34   7.329%   $69.0555   $69.06   $69.05   $69.10  
  Purchase #3 $105.97   11.820%   $118.4957   $118.50   $118.50   $118.50  
  Purchase #4 $52.53   6.220%   $55.7974   $55.80   $55.80   $55.80  
  Purchase #5 $87.65   12.488%   $98.5957   $98.60   $98.60   $98.60  
  Purchase #6 $204.29   13.707%   $232.292   $232.29   $232.30   $232.30  
  Purchase #7 $148.32   4.206%   $154.5583   $154.56   $154.55   $154.60  
  7 purchase totals = $856.58       $944.7241   $944.74   $944.75   $944.80