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 $73.61   4.388%   $76.84   $76.84   $76.85   $76.80  
  Purchase #2 $169.27   10.316%   $186.7319   $186.73   $186.75   $186.70  
  Purchase #3 $25.26   6.202%   $26.8266   $26.83   $26.85   $26.80  
  Purchase #4 $135.67   6.341%   $144.2728   $144.27   $144.25   $144.30  
  Purchase #5 $133.46   9.133%   $145.6489   $145.65   $145.65   $145.60  
  Purchase #6 $50.67   4.440%   $52.9197   $52.92   $52.90   $52.90  
  Purchase #7 $232.87   3.574%   $241.1928   $241.19   $241.20   $241.20  
  7 purchase totals = $820.81       $874.4327   $874.43   $874.45   $874.30