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 $85.42   9.667%   $93.6776   $93.68   $93.70   $93.70  
  Purchase #2 $198.50   12.831%   $223.9695   $223.97   $223.95   $224.00  
  Purchase #3 $24.37   4.361%   $25.4328   $25.43   $25.45   $25.40  
  Purchase #4 $176.61   4.667%   $184.8524   $184.85   $184.85   $184.90  
  Purchase #5 $220.99   6.401%   $235.1356   $235.14   $235.15   $235.10  
  Purchase #6 $227.39   4.666%   $238   $238.00   $238.00   $238.00  
  Purchase #7 $55.59   8.312%   $60.2106   $60.21   $60.20   $60.20  
  7 purchase totals = $988.87       $1,061.2785   $1,061.28   $1,061.30   $1,061.30