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 $34.97   3.703%   $36.2649   $36.26   $36.25   $36.30  
  Purchase #2 $155.75   4.663%   $163.0126   $163.01   $163.00   $163.00  
  Purchase #3 $184.67   11.370%   $205.667   $205.67   $205.65   $205.70  
  Purchase #4 $94.55   8.240%   $102.3409   $102.34   $102.35   $102.30  
  Purchase #5 $198.30   12.253%   $222.5977   $222.60   $222.60   $222.60  
  Purchase #6 $184.59   4.200%   $192.3428   $192.34   $192.35   $192.30  
  Purchase #7 $23.31   8.701%   $25.3382   $25.34   $25.35   $25.30  
  7 purchase totals = $876.14       $947.5641   $947.56   $947.55   $947.50