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 $161.37   9.274%   $176.3355   $176.34   $176.35   $176.30  
  Purchase #2 $202.42   5.442%   $213.4357   $213.44   $213.45   $213.40  
  Purchase #3 $165.32   5.266%   $174.0258   $174.03   $174.05   $174.00  
  Purchase #4 $156.28   11.836%   $174.7773   $174.78   $174.80   $174.80  
  Purchase #5 $153.31   9.287%   $167.5479   $167.55   $167.55   $167.50  
  Purchase #6 $37.29   6.623%   $39.7597   $39.76   $39.75   $39.80  
  Purchase #7 $75.73   3.572%   $78.4351   $78.44   $78.45   $78.40  
  7 purchase totals = $951.72       $1,024.3170   $1,024.34   $1,024.40   $1,024.20