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 $95.26   8.794%   $103.6372   $103.64   $103.65   $103.60  
  Purchase #2 $200.87   5.868%   $212.6571   $212.66   $212.65   $212.70  
  Purchase #3 $230.26   7.281%   $247.0252   $247.03   $247.05   $247.00  
  Purchase #4 $57.91   10.129%   $63.7757   $63.78   $63.80   $63.80  
  Purchase #5 $206.27   6.396%   $219.463   $219.46   $219.45   $219.50  
  Purchase #6 $66.72   13.820%   $75.9407   $75.94   $75.95   $75.90  
  Purchase #7 $116.43   3.788%   $120.8404   $120.84   $120.85   $120.80  
  7 purchase totals = $973.72       $1,043.3393   $1,043.35   $1,043.40   $1,043.30