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 $44.79   8.412%   $48.5577   $48.56   $48.55   $48.60  
  Purchase #2 $148.89   3.735%   $154.451   $154.45   $154.45   $154.50  
  Purchase #3 $128.91   7.565%   $138.662   $138.66   $138.65   $138.70  
  Purchase #4 $146.61   12.442%   $164.8512   $164.85   $164.85   $164.90  
  Purchase #5 $210.58   3.349%   $217.6323   $217.63   $217.65   $217.60  
  Purchase #6 $246.83   10.441%   $272.6015   $272.60   $272.60   $272.60  
  Purchase #7 $186.86   10.422%   $206.3345   $206.33   $206.35   $206.30  
  7 purchase totals = $1,113.47       $1,203.0902   $1,203.08   $1,203.10   $1,203.20