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 $216.99   3.102%   $223.721   $223.72   $223.70   $223.70  
  Purchase #2 $237.66   7.132%   $254.6099   $254.61   $254.60   $254.60  
  Purchase #3 $151.37   10.547%   $167.335   $167.34   $167.35   $167.30  
  Purchase #4 $35.81   11.731%   $40.0109   $40.01   $40.00   $40.00  
  Purchase #5 $240.93   10.590%   $266.4445   $266.44   $266.45   $266.40  
  Purchase #6 $49.39   3.141%   $50.9413   $50.94   $50.95   $50.90  
  Purchase #7 $244.54   8.352%   $264.964   $264.96   $264.95   $265.00  
  7 purchase totals = $1,176.69       $1,268.0266   $1,268.02   $1,268.00   $1,267.90