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 $58.96   4.489%   $61.6067   $61.61   $61.60   $61.60  
  Purchase #2 $201.57   6.595%   $214.8635   $214.86   $214.85   $214.90  
  Purchase #3 $244.32   5.505%   $257.7698   $257.77   $257.75   $257.80  
  Purchase #4 $83.30   7.444%   $89.5009   $89.50   $89.50   $89.50  
  Purchase #5 $142.84   11.207%   $158.8481   $158.85   $158.85   $158.80  
  Purchase #6 $151.99   6.705%   $162.1809   $162.18   $162.20   $162.20  
  Purchase #7 $219.36   7.740%   $236.3385   $236.34   $236.35   $236.30  
  7 purchase totals = $1,102.34       $1,181.1084   $1,181.11   $1,181.10   $1,181.10