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 $205.31   5.207%   $216.0005   $216.00   $216.00   $216.00  
  Purchase #2 $55.94   5.363%   $58.9401   $58.94   $58.95   $58.90  
  Purchase #3 $196.97   3.214%   $203.3006   $203.30   $203.30   $203.30  
  Purchase #4 $241.95   7.702%   $260.585   $260.59   $260.60   $260.60  
  Purchase #5 $52.58   5.726%   $55.5907   $55.59   $55.60   $55.60  
  Purchase #6 $198.92   6.688%   $212.2238   $212.22   $212.20   $212.20  
  Purchase #7 $8.83   7.228%   $9.4682   $9.47   $9.45   $9.50  
  7 purchase totals = $960.50       $1,016.1089   $1,016.11   $1,016.10   $1,016.10