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 $221.38   9.288%   $241.9418   $241.94   $241.95   $241.90  
  Purchase #2 $38.29   13.456%   $43.4423   $43.44   $43.45   $43.40  
  Purchase #3 $206.84   13.811%   $235.4067   $235.41   $235.40   $235.40  
  Purchase #4 $193.45   10.374%   $213.5185   $213.52   $213.50   $213.50  
  Purchase #5 $192.46   4.781%   $201.6615   $201.66   $201.65   $201.70  
  Purchase #6 $118.75   5.248%   $124.982   $124.98   $125.00   $125.00  
  Purchase #7 $31.66   9.312%   $34.6082   $34.61   $34.60   $34.60  
  7 purchase totals = $1,002.83       $1,095.5610   $1,095.56   $1,095.55   $1,095.50