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 $145.76   4.727%   $152.6501   $152.65   $152.65   $152.70  
  Purchase #2 $222.96   10.112%   $245.5057   $245.51   $245.50   $245.50  
  Purchase #3 $62.89   8.696%   $68.3589   $68.36   $68.35   $68.40  
  Purchase #4 $34.88   5.419%   $36.7701   $36.77   $36.75   $36.80  
  Purchase #5 $241.52   8.539%   $262.1434   $262.14   $262.15   $262.10  
  Purchase #6 $202.58   5.661%   $214.0481   $214.05   $214.05   $214.00  
  Purchase #7 $247.53   13.428%   $280.7683   $280.77   $280.75   $280.80  
  7 purchase totals = $1,158.12       $1,260.2446   $1,260.25   $1,260.20   $1,260.30