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 $86.84   7.669%   $93.4998   $93.50   $93.50   $93.50  
  Purchase #2 $169.56   9.279%   $185.2935   $185.29   $185.30   $185.30  
  Purchase #3 $8.51   9.462%   $9.3152   $9.32   $9.30   $9.30  
  Purchase #4 $186.56   3.192%   $192.515   $192.52   $192.50   $192.50  
  Purchase #5 $235.80   5.412%   $248.5615   $248.56   $248.55   $248.60  
  Purchase #6 $248.55   13.789%   $282.8226   $282.82   $282.80   $282.80  
  Purchase #7 $79.58   7.721%   $85.7244   $85.72   $85.70   $85.70  
  7 purchase totals = $1,015.40       $1,097.7320   $1,097.73   $1,097.65   $1,097.70