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 $152.46   5.753%   $161.231   $161.23   $161.25   $161.20  
  Purchase #2 $111.40   5.699%   $117.7487   $117.75   $117.75   $117.70  
  Purchase #3 $85.75   13.559%   $97.3768   $97.38   $97.40   $97.40  
  Purchase #4 $167.31   3.133%   $172.5518   $172.55   $172.55   $172.60  
  Purchase #5 $196.70   7.183%   $210.829   $210.83   $210.85   $210.80  
  Purchase #6 $181.71   5.652%   $191.9802   $191.98   $192.00   $192.00  
  Purchase #7 $75.42   10.547%   $83.3745   $83.37   $83.35   $83.40  
  7 purchase totals = $970.75       $1,035.0920   $1,035.09   $1,035.15   $1,035.10