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 $61.48   10.815%   $68.1291   $68.13   $68.15   $68.10  
  Purchase #2 $228.53   6.444%   $243.2565   $243.26   $243.25   $243.30  
  Purchase #3 $117.42   5.239%   $123.5716   $123.57   $123.55   $123.60  
  Purchase #4 $210.57   6.247%   $223.7243   $223.72   $223.70   $223.70  
  Purchase #5 $241.37   12.298%   $271.0537   $271.05   $271.05   $271.10  
  Purchase #6 $121.49   6.585%   $129.4901   $129.49   $129.50   $129.50  
  Purchase #7 $129.76   12.574%   $146.076   $146.08   $146.10   $146.10  
  7 purchase totals = $1,110.62       $1,205.3013   $1,205.30   $1,205.30   $1,205.40