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 $226.60   3.406%   $234.318   $234.32   $234.30   $234.30  
  Purchase #2 $219.32   8.449%   $237.8503   $237.85   $237.85   $237.90  
  Purchase #3 $12.27   9.341%   $13.4161   $13.42   $13.40   $13.40  
  Purchase #4 $99.73   5.773%   $105.4874   $105.49   $105.50   $105.50  
  Purchase #5 $169.47   8.869%   $184.5003   $184.50   $184.50   $184.50  
  Purchase #6 $166.27   6.845%   $177.6512   $177.65   $177.65   $177.70  
  Purchase #7 $103.35   6.212%   $109.7701   $109.77   $109.75   $109.80  
  7 purchase totals = $997.01       $1,062.9934   $1,063.00   $1,062.95   $1,063.10