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 $113.88   4.410%   $118.9021   $118.90   $118.90   $118.90  
  Purchase #2 $169.75   12.641%   $191.2081   $191.21   $191.20   $191.20  
  Purchase #3 $168.39   10.753%   $186.497   $186.50   $186.50   $186.50  
  Purchase #4 $182.60   5.381%   $192.4257   $192.43   $192.45   $192.40  
  Purchase #5 $232.99   8.607%   $253.0434   $253.04   $253.05   $253.00  
  Purchase #6 $243.80   12.710%   $274.787   $274.79   $274.80   $274.80  
  Purchase #7 $50.66   7.459%   $54.4387   $54.44   $54.45   $54.40  
  7 purchase totals = $1,162.07       $1,271.3020   $1,271.31   $1,271.35   $1,271.20