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 $53.34   12.200%   $59.8475   $59.85   $59.85   $59.80  
  Purchase #2 $182.41   10.650%   $201.8367   $201.84   $201.85   $201.80  
  Purchase #3 $147.41   3.562%   $152.6607   $152.66   $152.65   $152.70  
  Purchase #4 $169.51   3.436%   $175.3344   $175.33   $175.35   $175.30  
  Purchase #5 $173.49   5.226%   $182.5566   $182.56   $182.55   $182.60  
  Purchase #6 $174.30   9.106%   $190.1718   $190.17   $190.15   $190.20  
  Purchase #7 $218.78   6.343%   $232.6572   $232.66   $232.65   $232.70  
  7 purchase totals = $1,119.24       $1,195.0649   $1,195.07   $1,195.05   $1,195.10