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 $59.40   5.276%   $62.5339   $62.53   $62.55   $62.50  
  Purchase #2 $181.51   7.677%   $195.4445   $195.44   $195.45   $195.40  
  Purchase #3 $23.58   4.383%   $24.6135   $24.61   $24.60   $24.60  
  Purchase #4 $202.40   8.408%   $219.4178   $219.42   $219.40   $219.40  
  Purchase #5 $201.96   10.103%   $222.364   $222.36   $222.35   $222.40  
  Purchase #6 $47.45   6.444%   $50.5077   $50.51   $50.50   $50.50  
  Purchase #7 $227.89   8.509%   $247.2812   $247.28   $247.30   $247.30  
  7 purchase totals = $944.19       $1,022.1626   $1,022.15   $1,022.15   $1,022.10