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 $94.86   8.525%   $102.9468   $102.95   $102.95   $102.90  
  Purchase #2 $172.61   4.607%   $180.5621   $180.56   $180.55   $180.60  
  Purchase #3 $187.70   4.685%   $196.4937   $196.49   $196.50   $196.50  
  Purchase #4 $174.98   4.604%   $183.0361   $183.04   $183.05   $183.00  
  Purchase #5 $223.28   9.862%   $245.2999   $245.30   $245.30   $245.30  
  Purchase #6 $221.29   3.135%   $228.2274   $228.23   $228.25   $228.20  
  Purchase #7 $33.52   4.800%   $35.129   $35.13   $35.15   $35.10  
  7 purchase totals = $1,108.24       $1,171.6950   $1,171.70   $1,171.75   $1,171.60