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 $213.50   7.130%   $228.7226   $228.72   $228.70   $228.70  
  Purchase #2 $219.64   5.168%   $230.991   $230.99   $231.00   $231.00  
  Purchase #3 $238.32   11.706%   $266.2177   $266.22   $266.20   $266.20  
  Purchase #4 $162.62   13.548%   $184.6518   $184.65   $184.65   $184.70  
  Purchase #5 $225.30   5.264%   $237.1598   $237.16   $237.15   $237.20  
  Purchase #6 $152.40   6.165%   $161.7955   $161.80   $161.80   $161.80  
  Purchase #7 $124.66   8.793%   $135.6214   $135.62   $135.60   $135.60  
  7 purchase totals = $1,336.44       $1,445.1598   $1,445.16   $1,445.10   $1,445.20