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 $216.75   9.313%   $236.9359   $236.94   $236.95   $236.90  
  Purchase #2 $27.69   11.192%   $30.7891   $30.79   $30.80   $30.80  
  Purchase #3 $38.88   13.611%   $44.172   $44.17   $44.15   $44.20  
  Purchase #4 $160.28   6.621%   $170.8921   $170.89   $170.90   $170.90  
  Purchase #5 $235.48   3.362%   $243.3968   $243.40   $243.40   $243.40  
  Purchase #6 $110.72   11.586%   $123.548   $123.55   $123.55   $123.50  
  Purchase #7 $205.48   7.359%   $220.6013   $220.60   $220.60   $220.60  
  7 purchase totals = $995.28       $1,070.3352   $1,070.34   $1,070.35   $1,070.30