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 $113.87   3.627%   $118.0001   $118.00   $118.00   $118.00  
  Purchase #2 $198.46   3.723%   $205.8487   $205.85   $205.85   $205.80  
  Purchase #3 $43.33   6.307%   $46.0628   $46.06   $46.05   $46.10  
  Purchase #4 $200.52   4.785%   $210.1149   $210.11   $210.10   $210.10  
  Purchase #5 $149.51   4.773%   $156.6461   $156.65   $156.65   $156.60  
  Purchase #6 $79.69   5.804%   $84.3152   $84.32   $84.30   $84.30  
  Purchase #7 $118.69   7.690%   $127.8173   $127.82   $127.80   $127.80  
  7 purchase totals = $904.07       $948.8051   $948.81   $948.75   $948.70