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 $24.49   8.663%   $26.6116   $26.61   $26.60   $26.60  
  Purchase #2 $237.90   3.279%   $245.7007   $245.70   $245.70   $245.70  
  Purchase #3 $86.53   11.846%   $96.7803   $96.78   $96.80   $96.80  
  Purchase #4 $146.93   3.551%   $152.1475   $152.15   $152.15   $152.10  
  Purchase #5 $236.85   7.108%   $253.6853   $253.69   $253.70   $253.70  
  Purchase #6 $176.52   3.784%   $183.1995   $183.20   $183.20   $183.20  
  Purchase #7 $87.43   8.685%   $95.0233   $95.02   $95.00   $95.00  
  7 purchase totals = $996.65       $1,053.1482   $1,053.15   $1,053.15   $1,053.10