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 $162.61   8.559%   $176.5278   $176.53   $176.55   $176.50  
  Purchase #2 $199.35   5.788%   $210.8884   $210.89   $210.90   $210.90  
  Purchase #3 $75.36   7.429%   $80.9585   $80.96   $80.95   $81.00  
  Purchase #4 $225.44   12.755%   $254.1949   $254.19   $254.20   $254.20  
  Purchase #5 $240.97   7.331%   $258.6355   $258.64   $258.65   $258.60  
  Purchase #6 $235.34   5.310%   $247.8366   $247.84   $247.85   $247.80  
  Purchase #7 $206.88   3.604%   $214.336   $214.34   $214.35   $214.30  
  7 purchase totals = $1,345.95       $1,443.3777   $1,443.39   $1,443.45   $1,443.30