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 $83.32   3.853%   $86.5303   $86.53   $86.55   $86.50  
  Purchase #2 $237.72   3.796%   $246.7439   $246.74   $246.75   $246.70  
  Purchase #3 $94.96   11.765%   $106.132   $106.13   $106.15   $106.10  
  Purchase #4 $229.58   12.817%   $259.0053   $259.01   $259.00   $259.00  
  Purchase #5 $193.90   4.659%   $202.9338   $202.93   $202.95   $202.90  
  Purchase #6 $197.76   7.238%   $212.0739   $212.07   $212.05   $212.10  
  Purchase #7 $64.90   9.207%   $70.8753   $70.88   $70.90   $70.90  
  7 purchase totals = $1,102.14       $1,184.2945   $1,184.29   $1,184.35   $1,184.20