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 $118.58   5.644%   $125.2727   $125.27   $125.25   $125.30  
  Purchase #2 $179.74   7.121%   $192.5393   $192.54   $192.55   $192.50  
  Purchase #3 $238.53   6.826%   $254.8121   $254.81   $254.80   $254.80  
  Purchase #4 $136.34   9.261%   $148.9664   $148.97   $148.95   $149.00  
  Purchase #5 $16.69   3.602%   $17.2912   $17.29   $17.30   $17.30  
  Purchase #6 $134.49   8.170%   $145.4778   $145.48   $145.50   $145.50  
  Purchase #7 $158.84   11.841%   $177.6482   $177.65   $177.65   $177.60  
  7 purchase totals = $983.21       $1,062.0077   $1,062.01   $1,062.00   $1,062.00