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 $213.62   9.521%   $233.9588   $233.96   $233.95   $234.00  
  Purchase #2 $116.37   8.311%   $126.0415   $126.04   $126.05   $126.00  
  Purchase #3 $176.47   6.555%   $188.0376   $188.04   $188.05   $188.00  
  Purchase #4 $123.79   6.801%   $132.209   $132.21   $132.20   $132.20  
  Purchase #5 $38.51   12.102%   $43.1705   $43.17   $43.15   $43.20  
  Purchase #6 $189.84   5.500%   $200.2812   $200.28   $200.30   $200.30  
  Purchase #7 $225.39   6.262%   $239.5039   $239.50   $239.50   $239.50  
  7 purchase totals = $1,083.99       $1,163.2025   $1,163.20   $1,163.20   $1,163.20