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 $218.62   7.816%   $235.7073   $235.71   $235.70   $235.70  
  Purchase #2 $219.70   9.822%   $241.2789   $241.28   $241.30   $241.30  
  Purchase #3 $117.50   13.684%   $133.5787   $133.58   $133.60   $133.60  
  Purchase #4 $120.52   4.551%   $126.0049   $126.00   $126.00   $126.00  
  Purchase #5 $197.62   3.602%   $204.7383   $204.74   $204.75   $204.70  
  Purchase #6 $124.49   8.443%   $135.0007   $135.00   $135.00   $135.00  
  Purchase #7 $50.83   10.668%   $56.2525   $56.25   $56.25   $56.30  
  7 purchase totals = $1,049.28       $1,132.5613   $1,132.56   $1,132.60   $1,132.60