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 $162.26   13.367%   $183.9493   $183.95   $183.95   $183.90  
  Purchase #2 $193.50   3.461%   $200.197   $200.20   $200.20   $200.20  
  Purchase #3 $154.45   7.695%   $166.3349   $166.33   $166.35   $166.30  
  Purchase #4 $147.96   10.515%   $163.518   $163.52   $163.50   $163.50  
  Purchase #5 $101.29   6.512%   $107.886   $107.89   $107.90   $107.90  
  Purchase #6 $49.92   6.700%   $53.2646   $53.26   $53.25   $53.30  
  Purchase #7 $96.79   11.475%   $107.8967   $107.90   $107.90   $107.90  
  7 purchase totals = $906.17       $983.0465   $983.05   $983.05   $983.00