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 $162.50   8.673%   $176.5936   $176.59   $176.60   $176.60  
  Purchase #2 $118.64   8.743%   $129.0127   $129.01   $129.00   $129.00  
  Purchase #3 $85.95   6.791%   $91.7869   $91.79   $91.80   $91.80  
  Purchase #4 $215.81   5.343%   $227.3407   $227.34   $227.35   $227.30  
  Purchase #5 $192.28   7.220%   $206.1626   $206.16   $206.15   $206.20  
  Purchase #6 $188.77   13.432%   $214.1256   $214.13   $214.15   $214.10  
  Purchase #7 $16.31   7.409%   $17.5184   $17.52   $17.50   $17.50  
  7 purchase totals = $980.26       $1,062.5405   $1,062.54   $1,062.55   $1,062.50