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 $113.97   11.193%   $126.7267   $126.73   $126.75   $126.70  
  Purchase #2 $227.69   5.808%   $240.9142   $240.91   $240.90   $240.90  
  Purchase #3 $39.75   4.326%   $41.4696   $41.47   $41.45   $41.50  
  Purchase #4 $79.97   9.166%   $87.3001   $87.30   $87.30   $87.30  
  Purchase #5 $229.97   6.353%   $244.58   $244.58   $244.60   $244.60  
  Purchase #6 $165.75   9.413%   $181.352   $181.35   $181.35   $181.40  
  Purchase #7 $137.40   11.637%   $153.3892   $153.39   $153.40   $153.40  
  7 purchase totals = $994.50       $1,075.7318   $1,075.73   $1,075.75   $1,075.80