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 $44.58   8.711%   $48.4634   $48.46   $48.45   $48.50  
  Purchase #2 $244.70   8.280%   $264.9612   $264.96   $264.95   $265.00  
  Purchase #3 $98.72   10.697%   $109.2801   $109.28   $109.30   $109.30  
  Purchase #4 $233.78   10.694%   $258.7804   $258.78   $258.80   $258.80  
  Purchase #5 $225.92   3.515%   $233.8611   $233.86   $233.85   $233.90  
  Purchase #6 $235.50   7.234%   $252.5361   $252.54   $252.55   $252.50  
  Purchase #7 $40.36   9.344%   $44.1312   $44.13   $44.15   $44.10  
  7 purchase totals = $1,123.56       $1,212.0135   $1,212.01   $1,212.05   $1,212.10