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 $177.48   10.184%   $195.5546   $195.55   $195.55   $195.60  
  Purchase #2 $138.68   10.684%   $153.4966   $153.50   $153.50   $153.50  
  Purchase #3 $141.57   13.189%   $160.2417   $160.24   $160.25   $160.20  
  Purchase #4 $113.39   5.236%   $119.3271   $119.33   $119.35   $119.30  
  Purchase #5 $202.83   5.760%   $214.513   $214.51   $214.50   $214.50  
  Purchase #6 $140.49   5.418%   $148.1017   $148.10   $148.10   $148.10  
  Purchase #7 $155.75   7.835%   $167.953   $167.95   $167.95   $168.00  
  7 purchase totals = $1,070.19       $1,159.1877   $1,159.18   $1,159.20   $1,159.20