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 $24.58   5.590%   $25.954   $25.95   $25.95   $26.00  
  Purchase #2 $53.35   5.821%   $56.4555   $56.46   $56.45   $56.50  
  Purchase #3 $197.59   6.696%   $210.8206   $210.82   $210.80   $210.80  
  Purchase #4 $197.58   12.162%   $221.6097   $221.61   $221.60   $221.60  
  Purchase #5 $156.43   11.623%   $174.6119   $174.61   $174.60   $174.60  
  Purchase #6 $243.53   13.306%   $275.9341   $275.93   $275.95   $275.90  
  Purchase #7 $98.53   12.633%   $110.9773   $110.98   $111.00   $111.00  
  7 purchase totals = $971.59       $1,076.3631   $1,076.36   $1,076.35   $1,076.40