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 $152.41   7.493%   $163.8301   $163.83   $163.85   $163.80  
  Purchase #2 $123.97   10.153%   $136.5567   $136.56   $136.55   $136.60  
  Purchase #3 $150.39   11.132%   $167.1314   $167.13   $167.15   $167.10  
  Purchase #4 $228.38   9.656%   $250.4324   $250.43   $250.45   $250.40  
  Purchase #5 $198.95   6.662%   $212.204   $212.20   $212.20   $212.20  
  Purchase #6 $52.99   5.191%   $55.7407   $55.74   $55.75   $55.70  
  Purchase #7 $175.69   7.673%   $189.1707   $189.17   $189.15   $189.20  
  7 purchase totals = $1,082.78       $1,175.0660   $1,175.06   $1,175.10   $1,175.00