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 $86.29   11.364%   $96.096   $96.10   $96.10   $96.10  
  Purchase #2 $222.93   13.856%   $253.8192   $253.82   $253.80   $253.80  
  Purchase #3 $87.39   5.841%   $92.4944   $92.49   $92.50   $92.50  
  Purchase #4 $220.94   13.853%   $251.5468   $251.55   $251.55   $251.50  
  Purchase #5 $60.99   10.725%   $67.5312   $67.53   $67.55   $67.50  
  Purchase #6 $118.91   12.760%   $134.0829   $134.08   $134.10   $134.10  
  Purchase #7 $224.96   9.420%   $246.1512   $246.15   $246.15   $246.20  
  7 purchase totals = $1,022.41       $1,141.7217   $1,141.72   $1,141.75   $1,141.70