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 $91.65   3.175%   $94.5599   $94.56   $94.55   $94.60  
  Purchase #2 $153.68   10.759%   $170.2144   $170.21   $170.20   $170.20  
  Purchase #3 $236.53   7.279%   $253.747   $253.75   $253.75   $253.70  
  Purchase #4 $190.79   4.678%   $199.7152   $199.72   $199.70   $199.70  
  Purchase #5 $166.70   7.581%   $179.3375   $179.34   $179.35   $179.30  
  Purchase #6 $20.91   11.187%   $23.2492   $23.25   $23.25   $23.20  
  Purchase #7 $128.69   8.415%   $139.5193   $139.52   $139.50   $139.50  
  7 purchase totals = $988.95       $1,060.3425   $1,060.35   $1,060.30   $1,060.20