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 $96.27   7.620%   $103.6058   $103.61   $103.60   $103.60  
  Purchase #2 $80.79   9.722%   $88.6444   $88.64   $88.65   $88.60  
  Purchase #3 $186.40   6.697%   $198.8832   $198.88   $198.90   $198.90  
  Purchase #4 $246.98   6.390%   $262.762   $262.76   $262.75   $262.80  
  Purchase #5 $227.66   3.280%   $235.1272   $235.13   $235.15   $235.10  
  Purchase #6 $135.53   8.769%   $147.4146   $147.41   $147.40   $147.40  
  Purchase #7 $110.90   5.756%   $117.2834   $117.28   $117.30   $117.30  
  7 purchase totals = $1,084.53       $1,153.7206   $1,153.71   $1,153.75   $1,153.70