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 $87.43   10.197%   $96.3452   $96.35   $96.35   $96.30  
  Purchase #2 $81.72   12.489%   $91.926   $91.93   $91.95   $91.90  
  Purchase #3 $175.98   6.367%   $187.1846   $187.18   $187.20   $187.20  
  Purchase #4 $29.91   3.435%   $30.9374   $30.94   $30.95   $30.90  
  Purchase #5 $219.44   12.759%   $247.4383   $247.44   $247.45   $247.40  
  Purchase #6 $57.84   9.735%   $63.4707   $63.47   $63.45   $63.50  
  Purchase #7 $36.44   5.861%   $38.5757   $38.58   $38.60   $38.60  
  7 purchase totals = $688.76       $755.8779   $755.89   $755.95   $755.80