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 $174.51   5.336%   $183.8219   $183.82   $183.80   $183.80  
  Purchase #2 $218.89   6.306%   $232.6932   $232.69   $232.70   $232.70  
  Purchase #3 $50.62   3.207%   $52.2434   $52.24   $52.25   $52.20  
  Purchase #4 $69.44   6.380%   $73.8703   $73.87   $73.85   $73.90  
  Purchase #5 $247.30   6.355%   $263.0159   $263.02   $263.00   $263.00  
  Purchase #6 $96.88   5.431%   $102.1416   $102.14   $102.15   $102.10  
  Purchase #7 $229.26   5.126%   $241.0119   $241.01   $241.00   $241.00  
  7 purchase totals = $1,086.90       $1,148.7982   $1,148.79   $1,148.75   $1,148.70