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 $186.41   5.233%   $196.1648   $196.16   $196.15   $196.20  
  Purchase #2 $199.95   8.370%   $216.6858   $216.69   $216.70   $216.70  
  Purchase #3 $140.28   5.480%   $147.9673   $147.97   $147.95   $148.00  
  Purchase #4 $213.72   6.751%   $228.1482   $228.15   $228.15   $228.10  
  Purchase #5 $167.84   9.773%   $184.243   $184.24   $184.25   $184.20  
  Purchase #6 $69.53   11.499%   $77.5253   $77.53   $77.55   $77.50  
  Purchase #7 $76.38   9.460%   $83.6055   $83.61   $83.60   $83.60  
  7 purchase totals = $1,054.11       $1,134.3399   $1,134.35   $1,134.35   $1,134.30