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 $132.94   11.436%   $148.143   $148.14   $148.15   $148.10  
  Purchase #2 $209.85   3.697%   $217.6082   $217.61   $217.60   $217.60  
  Purchase #3 $168.27   10.331%   $185.654   $185.65   $185.65   $185.70  
  Purchase #4 $44.72   3.790%   $46.4149   $46.41   $46.40   $46.40  
  Purchase #5 $73.30   9.254%   $80.0832   $80.08   $80.10   $80.10  
  Purchase #6 $212.34   4.328%   $221.5301   $221.53   $221.55   $221.50  
  Purchase #7 $153.35   13.831%   $174.5598   $174.56   $174.55   $174.60  
  7 purchase totals = $994.77       $1,073.9932   $1,073.98   $1,074.00   $1,074.00