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 $33.55   6.173%   $35.621   $35.62   $35.60   $35.60  
  Purchase #2 $192.51   6.278%   $204.5958   $204.60   $204.60   $204.60  
  Purchase #3 $202.95   4.788%   $212.6672   $212.67   $212.65   $212.70  
  Purchase #4 $93.98   13.234%   $106.4173   $106.42   $106.40   $106.40  
  Purchase #5 $189.72   3.445%   $196.2559   $196.26   $196.25   $196.30  
  Purchase #6 $209.54   7.130%   $224.4802   $224.48   $224.50   $224.50  
  Purchase #7 $169.71   5.727%   $179.4293   $179.43   $179.45   $179.40  
  7 purchase totals = $1,091.96       $1,159.4667   $1,159.48   $1,159.45   $1,159.50