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 $61.72   10.274%   $68.0611   $68.06   $68.05   $68.10  
  Purchase #2 $212.98   7.614%   $229.1963   $229.20   $229.20   $229.20  
  Purchase #3 $246.36   4.459%   $257.3452   $257.35   $257.35   $257.30  
  Purchase #4 $142.41   7.430%   $152.9911   $152.99   $153.00   $153.00  
  Purchase #5 $45.70   3.151%   $47.14   $47.14   $47.15   $47.10  
  Purchase #6 $186.92   13.530%   $212.2103   $212.21   $212.20   $212.20  
  Purchase #7 $236.52   9.558%   $259.1266   $259.13   $259.15   $259.10  
  7 purchase totals = $1,132.61       $1,226.0706   $1,226.08   $1,226.10   $1,226.00