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 $167.94   4.411%   $175.3478   $175.35   $175.35   $175.30  
  Purchase #2 $48.53   12.424%   $54.5594   $54.56   $54.55   $54.60  
  Purchase #3 $216.59   13.719%   $246.304   $246.30   $246.30   $246.30  
  Purchase #4 $136.82   7.523%   $147.113   $147.11   $147.10   $147.10  
  Purchase #5 $113.77   6.515%   $121.1821   $121.18   $121.20   $121.20  
  Purchase #6 $140.71   11.356%   $156.689   $156.69   $156.70   $156.70  
  Purchase #7 $154.64   4.156%   $161.0668   $161.07   $161.05   $161.10  
  7 purchase totals = $979.00       $1,062.2621   $1,062.26   $1,062.25   $1,062.30