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 $222.76   13.281%   $252.3448   $252.34   $252.35   $252.30  
  Purchase #2 $207.57   6.760%   $221.6017   $221.60   $221.60   $221.60  
  Purchase #3 $88.94   4.655%   $93.0802   $93.08   $93.10   $93.10  
  Purchase #4 $243.94   6.416%   $259.5912   $259.59   $259.60   $259.60  
  Purchase #5 $162.82   5.783%   $172.2359   $172.24   $172.25   $172.20  
  Purchase #6 $228.70   6.330%   $243.1767   $243.18   $243.20   $243.20  
  Purchase #7 $146.31   4.807%   $153.3431   $153.34   $153.35   $153.30  
  7 purchase totals = $1,301.04       $1,395.3736   $1,395.37   $1,395.45   $1,395.30