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 $53.68   11.539%   $59.8741   $59.87   $59.85   $59.90  
  Purchase #2 $168.83   13.710%   $191.9766   $191.98   $192.00   $192.00  
  Purchase #3 $161.52   12.671%   $181.9862   $181.99   $182.00   $182.00  
  Purchase #4 $224.80   12.313%   $252.4796   $252.48   $252.50   $252.50  
  Purchase #5 $80.81   11.501%   $90.104   $90.10   $90.10   $90.10  
  Purchase #6 $217.26   6.175%   $230.6758   $230.68   $230.70   $230.70  
  Purchase #7 $138.88   5.689%   $146.7809   $146.78   $146.80   $146.80  
  7 purchase totals = $1,045.78       $1,153.8772   $1,153.88   $1,153.95   $1,154.00