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 $176.26   10.108%   $194.0764   $194.08   $194.10   $194.10  
  Purchase #2 $49.57   7.138%   $53.1083   $53.11   $53.10   $53.10  
  Purchase #3 $117.65   5.281%   $123.8631   $123.86   $123.85   $123.90  
  Purchase #4 $160.50   6.269%   $170.5617   $170.56   $170.55   $170.60  
  Purchase #5 $201.85   10.102%   $222.2409   $222.24   $222.25   $222.20  
  Purchase #6 $106.42   12.183%   $119.3851   $119.39   $119.40   $119.40  
  Purchase #7 $128.93   11.146%   $143.3005   $143.30   $143.30   $143.30  
  7 purchase totals = $941.18       $1,026.5360   $1,026.54   $1,026.55   $1,026.60