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 $33.94   3.178%   $35.0186   $35.02   $35.00   $35.00  
  Purchase #2 $104.71   5.505%   $110.4743   $110.47   $110.45   $110.50  
  Purchase #3 $202.91   5.489%   $214.0477   $214.05   $214.05   $214.00  
  Purchase #4 $138.84   6.148%   $147.3759   $147.38   $147.40   $147.40  
  Purchase #5 $123.56   6.284%   $131.3245   $131.32   $131.30   $131.30  
  Purchase #6 $185.32   6.567%   $197.49   $197.49   $197.50   $197.50  
  Purchase #7 $191.62   11.785%   $214.2024   $214.20   $214.20   $214.20  
  7 purchase totals = $980.90       $1,049.9334   $1,049.93   $1,049.90   $1,049.90