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 $41.74   6.777%   $44.5687   $44.57   $44.55   $44.60  
  Purchase #2 $167.85   3.683%   $174.0319   $174.03   $174.05   $174.00  
  Purchase #3 $191.35   13.356%   $216.9067   $216.91   $216.90   $216.90  
  Purchase #4 $195.30   10.255%   $215.328   $215.33   $215.35   $215.30  
  Purchase #5 $29.54   8.568%   $32.071   $32.07   $32.05   $32.10  
  Purchase #6 $52.56   4.633%   $54.9951   $55.00   $55.00   $55.00  
  Purchase #7 $247.69   11.844%   $277.0264   $277.03   $277.05   $277.00  
  7 purchase totals = $926.03       $1,014.9278   $1,014.94   $1,014.95   $1,014.90