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 $183.54   6.457%   $195.3912   $195.39   $195.40   $195.40  
  Purchase #2 $183.98   6.301%   $195.5726   $195.57   $195.55   $195.60  
  Purchase #3 $196.90   3.569%   $203.9274   $203.93   $203.95   $203.90  
  Purchase #4 $31.30   3.873%   $32.5122   $32.51   $32.50   $32.50  
  Purchase #5 $183.47   9.476%   $200.8556   $200.86   $200.85   $200.90  
  Purchase #6 $11.35   12.211%   $12.7359   $12.74   $12.75   $12.70  
  Purchase #7 $156.89   10.487%   $173.3431   $173.34   $173.35   $173.30  
  7 purchase totals = $947.43       $1,014.3380   $1,014.34   $1,014.35   $1,014.30