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 $191.52   4.463%   $200.0675   $200.07   $200.05   $200.10  
  Purchase #2 $41.53   5.224%   $43.6995   $43.70   $43.70   $43.70  
  Purchase #3 $154.84   12.403%   $174.0448   $174.04   $174.05   $174.00  
  Purchase #4 $148.28   13.487%   $168.2785   $168.28   $168.30   $168.30  
  Purchase #5 $89.83   4.325%   $93.7151   $93.72   $93.70   $93.70  
  Purchase #6 $218.62   4.700%   $228.8951   $228.90   $228.90   $228.90  
  Purchase #7 $157.76   3.435%   $163.1791   $163.18   $163.20   $163.20  
  7 purchase totals = $1,002.38       $1,071.8796   $1,071.89   $1,071.90   $1,071.90