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 $44.26   3.715%   $45.9043   $45.90   $45.90   $45.90  
  Purchase #2 $174.81   11.430%   $194.7908   $194.79   $194.80   $194.80  
  Purchase #3 $176.93   8.313%   $191.6382   $191.64   $191.65   $191.60  
  Purchase #4 $242.55   6.427%   $258.1387   $258.14   $258.15   $258.10  
  Purchase #5 $221.97   3.870%   $230.5602   $230.56   $230.55   $230.60  
  Purchase #6 $61.61   8.846%   $67.06   $67.06   $67.05   $67.10  
  Purchase #7 $42.51   7.201%   $45.5711   $45.57   $45.55   $45.60  
  7 purchase totals = $964.64       $1,033.6633   $1,033.66   $1,033.65   $1,033.70