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 $38.61   13.584%   $43.8548   $43.85   $43.85   $43.90  
  Purchase #2 $229.33   13.381%   $260.0166   $260.02   $260.00   $260.00  
  Purchase #3 $174.44   4.144%   $181.6688   $181.67   $181.65   $181.70  
  Purchase #4 $119.94   13.152%   $135.7145   $135.71   $135.70   $135.70  
  Purchase #5 $110.55   12.309%   $124.1576   $124.16   $124.15   $124.20  
  Purchase #6 $160.99   5.242%   $169.4291   $169.43   $169.45   $169.40  
  Purchase #7 $219.73   5.820%   $232.5183   $232.52   $232.50   $232.50  
  7 purchase totals = $1,053.59       $1,147.3597   $1,147.36   $1,147.30   $1,147.40