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 $82.85   13.805%   $94.2874   $94.29   $94.30   $94.30  
  Purchase #2 $223.65   12.479%   $251.5593   $251.56   $251.55   $251.60  
  Purchase #3 $62.93   4.505%   $65.765   $65.77   $65.75   $65.80  
  Purchase #4 $244.52   3.316%   $252.6283   $252.63   $252.65   $252.60  
  Purchase #5 $174.77   13.379%   $198.1525   $198.15   $198.15   $198.20  
  Purchase #6 $5.26   9.500%   $5.7597   $5.76   $5.75   $5.80  
  Purchase #7 $167.81   7.666%   $180.6743   $180.67   $180.65   $180.70  
  7 purchase totals = $961.79       $1,048.8265   $1,048.83   $1,048.80   $1,049.00