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 $202.98   11.585%   $226.4952   $226.50   $226.50   $226.50  
  Purchase #2 $196.60   7.834%   $212.0016   $212.00   $212.00   $212.00  
  Purchase #3 $176.48   4.682%   $184.7428   $184.74   $184.75   $184.70  
  Purchase #4 $153.73   9.357%   $168.1145   $168.11   $168.10   $168.10  
  Purchase #5 $244.99   9.545%   $268.3743   $268.37   $268.35   $268.40  
  Purchase #6 $189.52   5.346%   $199.6517   $199.65   $199.65   $199.70  
  Purchase #7 $197.85   5.631%   $208.9909   $208.99   $209.00   $209.00  
  7 purchase totals = $1,362.15       $1,468.3710   $1,468.36   $1,468.35   $1,468.40