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 $119.75   5.237%   $126.0213   $126.02   $126.00   $126.00  
  Purchase #2 $172.46   11.250%   $191.8618   $191.86   $191.85   $191.90  
  Purchase #3 $221.52   3.499%   $229.271   $229.27   $229.25   $229.30  
  Purchase #4 $230.47   13.150%   $260.7768   $260.78   $260.80   $260.80  
  Purchase #5 $181.63   10.844%   $201.326   $201.33   $201.35   $201.30  
  Purchase #6 $122.98   12.343%   $138.1594   $138.16   $138.15   $138.20  
  Purchase #7 $34.87   7.630%   $37.5306   $37.53   $37.55   $37.50  
  7 purchase totals = $1,083.68       $1,184.9469   $1,184.95   $1,184.95   $1,185.00