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 $37.93   8.241%   $41.0558   $41.06   $41.05   $41.10  
  Purchase #2 $220.84   9.763%   $242.4006   $242.40   $242.40   $242.40  
  Purchase #3 $81.89   8.368%   $88.7426   $88.74   $88.75   $88.70  
  Purchase #4 $211.61   9.173%   $231.021   $231.02   $231.00   $231.00  
  Purchase #5 $55.61   6.734%   $59.3548   $59.35   $59.35   $59.40  
  Purchase #6 $239.76   6.462%   $255.2533   $255.25   $255.25   $255.30  
  Purchase #7 $229.62   11.360%   $255.7048   $255.70   $255.70   $255.70  
  7 purchase totals = $1,077.26       $1,173.5329   $1,173.52   $1,173.50   $1,173.60