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 $146.66   5.414%   $154.6002   $154.60   $154.60   $154.60  
  Purchase #2 $10.48   12.249%   $11.7637   $11.76   $11.75   $11.80  
  Purchase #3 $61.76   3.399%   $63.8592   $63.86   $63.85   $63.90  
  Purchase #4 $247.47   11.461%   $275.8325   $275.83   $275.85   $275.80  
  Purchase #5 $247.86   8.657%   $269.3172   $269.32   $269.30   $269.30  
  Purchase #6 $205.55   5.424%   $216.699   $216.70   $216.70   $216.70  
  Purchase #7 $102.75   6.273%   $109.1955   $109.20   $109.20   $109.20  
  7 purchase totals = $1,022.53       $1,101.2673   $1,101.27   $1,101.25   $1,101.30