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 $52.57   11.198%   $58.4568   $58.46   $58.45   $58.50  
  Purchase #2 $181.52   4.681%   $190.017   $190.02   $190.00   $190.00  
  Purchase #3 $120.83   4.295%   $126.0196   $126.02   $126.00   $126.00  
  Purchase #4 $94.26   8.186%   $101.9761   $101.98   $102.00   $102.00  
  Purchase #5 $250.65   11.830%   $280.3019   $280.30   $280.30   $280.30  
  Purchase #6 $207.69   5.378%   $218.8596   $218.86   $218.85   $218.90  
  Purchase #7 $211.28   13.866%   $240.5761   $240.58   $240.60   $240.60  
  7 purchase totals = $1,118.80       $1,216.2071   $1,216.22   $1,216.20   $1,216.30