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 $195.65   6.159%   $207.7001   $207.70   $207.70   $207.70  
  Purchase #2 $246.95   9.262%   $269.8225   $269.82   $269.80   $269.80  
  Purchase #3 $64.56   12.391%   $72.5596   $72.56   $72.55   $72.60  
  Purchase #4 $170.82   6.776%   $182.3948   $182.39   $182.40   $182.40  
  Purchase #5 $198.62   12.270%   $222.9907   $222.99   $223.00   $223.00  
  Purchase #6 $101.61   4.245%   $105.9233   $105.92   $105.90   $105.90  
  Purchase #7 $59.62   7.142%   $63.8781   $63.88   $63.90   $63.90  
  7 purchase totals = $1,037.83       $1,125.2691   $1,125.26   $1,125.25   $1,125.30