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 $184.71   12.440%   $207.6879   $207.69   $207.70   $207.70  
  Purchase #2 $202.26   3.114%   $208.5584   $208.56   $208.55   $208.60  
  Purchase #3 $62.64   8.731%   $68.1091   $68.11   $68.10   $68.10  
  Purchase #4 $133.89   8.209%   $144.881   $144.88   $144.90   $144.90  
  Purchase #5 $221.27   10.854%   $245.2866   $245.29   $245.30   $245.30  
  Purchase #6 $22.98   10.161%   $25.315   $25.32   $25.30   $25.30  
  Purchase #7 $167.78   4.198%   $174.8234   $174.82   $174.80   $174.80  
  7 purchase totals = $995.53       $1,074.6614   $1,074.67   $1,074.65   $1,074.70