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 $64.75   6.515%   $68.9685   $68.97   $68.95   $69.00  
  Purchase #2 $204.44   6.327%   $217.3749   $217.37   $217.35   $217.40  
  Purchase #3 $241.69   9.706%   $265.1484   $265.15   $265.15   $265.10  
  Purchase #4 $227.88   13.216%   $257.9966   $258.00   $258.00   $258.00  
  Purchase #5 $209.74   5.612%   $221.5106   $221.51   $221.50   $221.50  
  Purchase #6 $179.28   4.112%   $186.652   $186.65   $186.65   $186.70  
  Purchase #7 $147.30   3.821%   $152.9283   $152.93   $152.95   $152.90  
  7 purchase totals = $1,275.08       $1,370.5793   $1,370.58   $1,370.55   $1,370.60