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 $56.70   9.345%   $61.9986   $62.00   $62.00   $62.00  
  Purchase #2 $194.84   5.241%   $205.0516   $205.05   $205.05   $205.10  
  Purchase #3 $57.96   7.142%   $62.0995   $62.10   $62.10   $62.10  
  Purchase #4 $248.64   5.151%   $261.4474   $261.45   $261.45   $261.40  
  Purchase #5 $32.30   6.320%   $34.3414   $34.34   $34.35   $34.30  
  Purchase #6 $156.72   7.263%   $168.1026   $168.10   $168.10   $168.10  
  Purchase #7 $221.54   4.620%   $231.7751   $231.78   $231.80   $231.80  
  7 purchase totals = $968.70       $1,024.8162   $1,024.82   $1,024.85   $1,024.80