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 $96.67   7.869%   $104.277   $104.28   $104.30   $104.30  
  Purchase #2 $158.69   12.380%   $178.3358   $178.34   $178.35   $178.30  
  Purchase #3 $54.83   7.234%   $58.7964   $58.80   $58.80   $58.80  
  Purchase #4 $189.76   6.730%   $202.5308   $202.53   $202.55   $202.50  
  Purchase #5 $75.83   6.444%   $80.7165   $80.72   $80.70   $80.70  
  Purchase #6 $185.69   6.415%   $197.602   $197.60   $197.60   $197.60  
  Purchase #7 $236.70   6.812%   $252.824   $252.82   $252.80   $252.80  
  7 purchase totals = $998.17       $1,075.0825   $1,075.09   $1,075.10   $1,075.00