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 $113.97   10.238%   $125.6382   $125.64   $125.65   $125.60  
  Purchase #2 $167.83   4.457%   $175.3102   $175.31   $175.30   $175.30  
  Purchase #3 $158.43   7.675%   $170.5895   $170.59   $170.60   $170.60  
  Purchase #4 $162.38   11.526%   $181.0959   $181.10   $181.10   $181.10  
  Purchase #5 $173.45   6.617%   $184.9272   $184.93   $184.95   $184.90  
  Purchase #6 $135.47   7.698%   $145.8985   $145.90   $145.90   $145.90  
  Purchase #7 $87.61   5.437%   $92.3734   $92.37   $92.35   $92.40  
  7 purchase totals = $999.14       $1,075.8329   $1,075.84   $1,075.85   $1,075.80