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 $194.53   3.659%   $201.6479   $201.65   $201.65   $201.60  
  Purchase #2 $246.31   10.771%   $272.8401   $272.84   $272.85   $272.80  
  Purchase #3 $62.93   3.312%   $65.0142   $65.01   $65.00   $65.00  
  Purchase #4 $229.57   6.556%   $244.6206   $244.62   $244.60   $244.60  
  Purchase #5 $206.94   5.146%   $217.5891   $217.59   $217.60   $217.60  
  Purchase #6 $35.75   6.387%   $38.0334   $38.03   $38.05   $38.00  
  Purchase #7 $72.65   3.540%   $75.2218   $75.22   $75.20   $75.20  
  7 purchase totals = $1,048.68       $1,114.9671   $1,114.96   $1,114.95   $1,114.80