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 $148.44   7.818%   $160.045   $160.05   $160.05   $160.00  
  Purchase #2 $184.86   8.187%   $199.9945   $199.99   $200.00   $200.00  
  Purchase #3 $156.57   6.708%   $167.0727   $167.07   $167.05   $167.10  
  Purchase #4 $191.80   9.718%   $210.4391   $210.44   $210.45   $210.40  
  Purchase #5 $179.41   11.867%   $200.7006   $200.70   $200.70   $200.70  
  Purchase #6 $248.39   11.268%   $276.3786   $276.38   $276.40   $276.40  
  Purchase #7 $225.31   7.224%   $241.5864   $241.59   $241.60   $241.60  
  7 purchase totals = $1,334.78       $1,456.2169   $1,456.22   $1,456.25   $1,456.20