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 $117.46   7.486%   $126.2531   $126.25   $126.25   $126.30  
  Purchase #2 $216.52   8.797%   $235.5673   $235.57   $235.55   $235.60  
  Purchase #3 $223.66   13.511%   $253.8787   $253.88   $253.90   $253.90  
  Purchase #4 $189.98   7.116%   $203.499   $203.50   $203.50   $203.50  
  Purchase #5 $192.56   3.862%   $199.9967   $200.00   $200.00   $200.00  
  Purchase #6 $222.85   11.580%   $248.656   $248.66   $248.65   $248.70  
  Purchase #7 $151.77   10.268%   $167.3537   $167.35   $167.35   $167.40  
  7 purchase totals = $1,314.80       $1,435.2045   $1,435.21   $1,435.20   $1,435.40